How much does building a custom web app actually cost?

The most common answer you'll get from a development agency when you ask this question is "it depends." That's technically true and practically useless.

Here are real numbers, with context for what pushes costs in each direction.

The honest ranges

| Type of application | Typical budget | Timeline | |---------------------|---------------|----------| | Internal tool (1-2 users, simple logic) | €5,000–12,000 | 4-8 weeks | | Small customer-facing app | €12,000–30,000 | 8-14 weeks | | Mid-size SaaS or platform | €30,000–80,000 | 14-28 weeks | | Complex platform (marketplace, multi-tenant, etc.) | €80,000+ | 6+ months |

These assume a competent small team (1-2 developers + design). Enterprise agencies with larger teams and more process overhead will quote higher. Offshore teams will quote lower, with corresponding trade-offs in communication and quality control.

What actually drives the cost

Scope ambiguity

The biggest hidden cost in custom development is unclear requirements. When you change direction mid-project — adding features, removing them, rethinking flows — you pay in rework. A well-defined spec before development starts is worth more than any individual technical choice.

Practical advice: Before asking for a quote, write down exactly what the app needs to do. User flows, data inputs and outputs, integrations. The more specific you are, the more accurate the quote.

Authentication and user management

Every app that has users — login, roles, permissions, password resets — adds €2,000-8,000 to the scope depending on complexity. Multi-tenant systems (where each customer has their own data space) add more.

Integrations

Every external service you need to connect adds scope. A Stripe integration for payments, a Brevo or SendGrid for email, a Slack webhook for notifications — each is 1-3 days of work. List your integrations upfront.

Admin panels

If someone needs to manage data through a back-office interface, that's essentially a second application running alongside the main one. Budget accordingly.

Mobile responsiveness vs native app

A responsive web app works on mobile browsers at no extra cost. A native iOS or Android app is a separate project. If someone says "and we'll also need an app," the budget typically doubles.

Real-time features

Live updates, notifications, collaborative editing — anything that requires a persistent connection between client and server is significantly more complex than standard request-response flows. Add 30-50% to your estimate if you need this.

What you don't need (and often get sold anyway)

Microservices architecture for an app that will have 50 users. It's overengineering that adds complexity and cost without benefit.

Mobile apps on day one. Build the web app, validate with users, then decide if native apps justify the investment.

A design system when you could use a component library. Design systems are for teams building multiple products. For a single app, it's premature.

Blockchain, AI integration, "future-proofing" without a specific use case. Each of these adds significant cost and complexity. Only add them if you can articulate exactly why.

How to get a useful quote

Agencies quote based on risk. The more uncertainty in your specification, the more buffer they add. To get an accurate quote:

1. Write a requirements document, even a rough one
2. Include user personas — who uses this and what do they need to do
3. Specify integrations you know you need
4. Note any regulatory requirements (GDPR data handling, industry compliance)
5. Distinguish "must have" from "nice to have"

Then ask for a fixed-price quote on the "must have" scope with a separate rate for additions. This gives you a reliable baseline.

Our approach

At Krokanti Software, we build our own SaaS products alongside client work — k-notes, k-tasks, k-cv — so we understand what it costs to build things properly and where to cut without cutting quality.

We'll tell you if your spec needs more work before we quote it. An inaccurate quote helps no one.

If you have a project in mind and want an honest assessment of scope and cost, get in touch.