What budget should you plan for a custom web application?

What determines the cost

• Business rules: statuses, approvals, calculations, exceptions. This is the most underestimated item.
• User profiles and their permissions: an internal tool for three people does not have the same requirements as a customer portal.
• Integrations: accounting, CRM, ERP, payment, e-signature, partner APIs.
• Data migration from spreadsheets or old software.
• Requirements for security, traceability and availability.

Orders of magnitude

As a guide, excluding VAT, for professional development in France:

• Targeted internal tool (one process, a few screens): €15,000 to €40,000.
• Business platform (several profiles, workflows, dashboards): €40,000 to €120,000.
• Platform open to customers, with payment or subscriptions: more, depending on scope.

These figures only make sense once the need has been described. A scoping phase of a few days often halves the uncertainty.

Reducing risk: start small, but start right

The safest method is to deliver the core of the process first, actually used, and then extend it. In practice:

1. map the current process and its pain points;
2. identify what truly creates value in the first version;
3. deliver that version, get it used, measure;
4. prioritise changes based on real feedback rather than assumptions.

This is the approach we follow in our methodology.

Running costs

An application lives on. Plan a yearly budget for hosting, corrective maintenance and security updates, plus an envelope for improvements. A simple rule: setting aside 15 to 20% of the initial cost each year keeps the tool from ageing until it has to be rebuilt.

Custom or existing software?

Before investing, check that no software on the market already covers 80% of the need. If it does, adapting or connecting it is often more cost-effective. Custom development makes full sense when your process is a competitive advantage. See our web application page.