This is the question we hear most often at INYSTER. And that makes perfect sense: before committing budget to a development project, you need to know what you’re getting into financially.
At INYSTER, we prefer transparency over opaque quotes. This guide covers the realistic price ranges we see on the French market in 2026 — POC, MVP, full application, client portal, AI automation. We add three costed scenarios by project typology, the variation factors, an enriched freelancer/agency/consultancy comparison, and the hidden costs too often forgotten in initial quotes. A concise FAQ closes the article on the questions that come up most often.
The main price ranges in 2026
POC (Proof of Concept): 8,000 — 15,000 EUR
A POC is designed to prove the technical feasibility and business value of an idea. In 2 to 4 weeks, you get a functional prototype that answers the question: “Can this actually work?”
What it includes: requirements scoping, mockups, functional prototype, documentation of what was tested and validated.
What it does not include: production environment, load handling, fine-grained role management, security audit, maintenance. A POC is a decision tool, not production software.
A concrete example from our portfolio: the Silot project (bulk product label generation) was delivered in 3 weeks as a business validation. The client was able to demonstrate real-world usage before committing to a full version. This kind of deliverable unlocks larger internal budget on the basis of a tangible prototype rather than a slide deck.
MVP (Minimum Viable Product): 15,000 — 30,000 EUR
The MVP goes further: it’s a simplified but usable version of your application. Robust enough to be tested by real users, lightweight enough to be delivered in 4 to 8 weeks.
What it includes: application architecture, front-end and back-end development, database, deployment, technical documentation.
Typical budget breakdown of a 20,000 EUR MVP: roughly 40% front-end (interfaces, interactions), 35% back-end (API, business logic), 15% database and deployment, 10% tests and documentation. A standard client-portal MVP — authentication, dashboard, 2-3 business workflows, one external API integration — comes out around 20,000 EUR.
Full application: 30,000 — 80,000+ EUR
The complete custom web application development with all features, integrations, fine-grained user management, production deployment, and post-launch support.
Timeline varies from 2 to 6 months depending on complexity. What tips a project past 80,000 EUR: multi-role management with granular permissions, multiple integrations (ERP, CRM, third-party business APIs), strict SLA requirements, external security audit, significant existing-data migration, industry compliance obligations (healthcare, finance, public sector).
Three costed scenarios by project type
To help calibrate a budget, here are three concrete scenarios observed on the French market in 2026, with the ranges we work with at INYSTER (EUR throughout — this is France-centered pricing).
Scenario 1 — Replace a critical Excel with a multi-user application: 18,000 — 25,000 EUR, 6 to 8 weeks
Typical context: an Excel or Google Sheet has become the backbone of a business process (order tracking, stock management, HR planning). It breaks regularly, multiple people edit it simultaneously, and errors are costly.
What we deliver: a multi-user web application with authentication, simple roles (user / admin), the same operations as Excel but made reliable, modification history, CSV export so you keep control. OVH hosting, daily backup.
The breakdown: 1 senior architect over 6 weeks of development, 1 week of user testing, 1 week of deployment and training. References for this kind of project in our portfolio of client cases include the internal client directory with KPIs and the restaurant Click & Collect.
Scenario 2 — AI-powered invoicing automation: 35,000 — 55,000 EUR, 3 to 4 months
Typical context: supplier invoices arrive as PDFs, are manually re-entered into accounting software, and checks (purchase order, receipt) happen downstream with frequent misses.
What we deliver: OCR + LLM pipeline to extract invoice data, automatic matching rules against purchase orders, multi-level validation workflow, direct accounting-software integration, tracking dashboard. A project like this combines custom development with AI building blocks — it’s a good candidate for a progressive approach: you can also automate a simpler business process in parallel to rehearse the method.
The breakdown: business scoping and invoice audit (3 weeks), OCR + AI pipeline development (6 weeks), accounting integration and workflow (4 weeks), UAT and production rollout (3 weeks). For more text-data-oriented projects, see our guide on RAG for business.
Scenario 3 — SaaS-like client portal: 50,000 — 80,000 EUR, 4 to 6 months
Typical context: a company wants to offer its clients self-service access to their data — orders, invoices, documents, support requests, intervention tracking. The goal: reduce support load and improve client experience.
What we deliver: multi-tenant authentication, per-client personalized dashboards, document space, billing module, notifications, API for future integrations. Architecture built to scale and evolve.
Experience to share: some of our clients have trusted us for more than 10 years on this kind of platform, with continuous iterations. Here’s what one of them says about working with us:
“A reliable and responsive partner who is a pleasure to work with. Beyond simply responding to our requests, he also anticipates needs and regularly proposes solutions we hadn’t thought of. I recommend without hesitation.”
— David, Operations Manager, LifeScan (Pharmaceutical Group)
This kind of long-term relationship changes the nature of the cost: year-2 and year-3 evolutions are cheaper because the architecture, domain knowledge, and technical debt are under control.
Factors that affect pricing
Several elements directly influence the final cost beyond the initial functional scope:
- Functional complexity: a simple dashboard vs. a multi-role application with approval workflows.
- Integrations: connecting to an ERP, CRM, or third-party API systematically adds work.
- Expected user volume: 10 internal users, 500 active clients, or 5,000 public users require very different architectures.
- Data volume: an application processing millions of rows requires a dedicated architecture, not a standard PostgreSQL instance.
- Security requirements: regulated industries (healthcare, finance, public sector) mean non-negotiable extra constraints.
- GDPR and data sovereignty: France / EU / on-premise hosting depending on data sensitivity.
- Mobile scope: responsive web (included), PWA (moderate cost), or native iOS/Android app (x2 to x3 on the mobile scope).
- Existing data migration: a clean import from Excel or a legacy database can represent 10-20% of the budget.
- Design: standard interface using our component system vs. fully bespoke design with dedicated mockups.
- Post-production maintenance: often forgotten from the initial quote. Our support offering starts at 300 EUR/month for INYSTER projects.
Freelancer, boutique agency, or IT consultancy — impact on price
Rates vary significantly depending on the type of provider. Here’s what we observe on the French market in 2026:
| Type | Daily rate | Best for | Risk |
|---|---|---|---|
| Junior freelancer | 300-500 EUR | Mockups, CMS tweaks, small scoped tasks | Turnover, no long-term architecture |
| Senior freelancer | 600-900 EUR | Short well-scoped missions, specific expertise | No team for follow-up, bus factor 1 |
| Boutique agency (INYSTER) | 500-800 EUR | POC to production, SMEs without CTO, strategic projects | Limited capacity — we select our projects |
| IT consultancy / large firm | 800-1,500 EUR | 500,000 EUR+ projects, multi-CIO, large enterprises | Management overhead, team rotation, juniors staffed silently |
Why daily rate isn’t the right KPI. A senior developer at 700 EUR/day delivering in 20 days costs 14,000 EUR and produces maintainable code. A junior at 400 EUR/day taking 50 days costs 20,000 EUR for a more fragile result. The right KPI is the total cost to reach a production deliverable — not the daily price.
Hidden costs to anticipate
Initial quotes often overlook five cost lines that genuinely weigh on the application’s total cost of ownership:
- Hosting and infrastructure: between 50 and 300 EUR per month depending on volume and redundancy needs. For a critical multi-user application, budget at least 150 EUR/month with proper backups and monitoring.
- Third-party licences: Stripe (1.4% + 0.25 EUR per transaction), email services (20-100 EUR/month), OpenAI or Anthropic API (variable with usage), OCR services, SMS providers. These costs start low and scale with usage.
- Corrective and evolutionary maintenance: the market standard is 15-20% of development cost per year. For a 40,000 EUR project, plan for 6,000-8,000 EUR annually.
- User training: often forgotten in quotes. A live training session plus video documentation typically represents 1,500-3,000 EUR and heavily drives adoption.
- Post-6-month evolutions: almost always necessary. Users uncover needs once the application is in their hands. We recommend reserving 20% of the initial budget for year-one evolutions.
Our approach at INYSTER
We consistently recommend starting with a POC before investing in full-scale development. This approach offers concrete advantages:
- You validate feasibility and business value before committing a significant budget.
- The POC is built on a scalable architecture: when you move to production, we don’t start from scratch.
- You have a concrete deliverable in 2-4 weeks to build internal buy-in or unlock additional budget.
INYSTER positions itself as a boutique agency: no outsourcing, one senior architect from first call to production. Our daily rate sits between 500 and 800 EUR depending on project complexity, with full transparency on what’s included in each fixed-price engagement. To explore our custom web development services or a more targeted mission, the first 30-minute call is free and dedicated to scope clarification.
Conclusion
The budget for a custom web application depends on many factors, but the most common range for a French SME falls between 15,000 EUR and 80,000 EUR for a first production version, with a median around 30,000 EUR for well-scoped projects.
The most common mistake isn’t under-budgeting — it’s skipping the POC step to validate the need before investing heavily. Failed projects are almost never poorly developed projects — they’re poorly scoped projects, or projects that didn’t match a real user need.
Got a project in mind? We scope and estimate your idea for free in 30 minutes and give you the realistic range to expect, with no commitment. Book a call.
Also read:
- POC vs MVP: which approach should you choose?
- Custom vs SaaS: how to choose?
- 5 signs your business process needs a dedicated tool
- n8n business automation: practical guide
- RAG for business: integrating AI with your data
Written by the INYSTER team. Christopher, founder and software architect, has 14+ years of experience designing custom business applications and supports French SMEs from idea to production.
Frequently asked questions
Why is there such a gap between two quotes for the same project?
The gap rarely comes from the daily rate. It comes from the implicit scope: two providers can quote the same brief with radically different assumptions about architecture, testing, security, maintenance, and data migration. A 20,000 EUR quote without tests or documentation isn't comparable to a 35,000 EUR quote including CI/CD, monitoring, tests, and training. Always ask for the detailed list of deliverables, not just the total.
What's the difference between fixed-price and time-and-materials?
In fixed-price, the provider commits to a defined scope, timeline, and price: ideal for well-scoped projects (POC, MVP). In time-and-materials, you pay per day worked: ideal for projects that evolve significantly or exploratory phases. At INYSTER, we favor fixed-price for POCs and MVPs, and a blend of fixed-price and T&M for long-running evolution work.
How much does custom web application maintenance cost?
Maintenance of a production web application typically represents 15-20% of the initial development cost per year, covering bug fixes, security updates, minor evolutions, and monitoring. For a 30,000 EUR application, plan for 4,500-6,000 EUR annually. Our support offering starts at 300 EUR/month for projects delivered by INYSTER.
Can we start small and scale up?
Yes, and it's the approach we consistently recommend. An 8,000-15,000 EUR POC validates feasibility in 2-4 weeks. If built on a scalable architecture, it becomes the foundation of the MVP and then the full application without rewrite. The mistake to avoid: going straight to a 50,000 EUR full application without validating real-world usage.
How much does a custom client portal cost?
A custom client portal (multi-tenant authentication, dashboards, document spaces, billing, notifications) typically falls between 50,000 and 80,000 EUR for a first production version, delivered in 4-6 months. Simpler portals (no multi-tenant, no integrated billing) can start at 30,000 EUR.
Is a 15,000 EUR MVP realistic in 2026?
Yes, provided the scope is genuinely minimal: a single use case, simple authentication, two or three functional screens, standard deployment. 15,000 EUR corresponds to roughly 20-25 days of senior development. Beyond that (multiple workflows, third-party integrations, complex roles), the MVP budget shifts into the 20-30,000 EUR range.