The verdict in three sentences
A custom React / Next.js app is quoted in 2026 between 45,000 and 160,000 EUR, with TypeScript, tests, CI/CD and cloud hosting. The "invisible" share — tests, observability, DevOps — is 25 to 35% of the budget but slashes the 3-year maintenance cost. Paying less by cutting that share just moves the bill to tomorrow, usually with interest.
Stack, tests and DevOps: their share of the budget
The sticker price hides the real effort split. A healthy quote makes that breakdown explicit.
| Item | What it covers | Budget share | Order of magnitude (80,000 EUR app) |
|---|---|---|---|
| Frontend (React/Next.js) | UI, SSR/SSG, routing, state | 25-35% | 20,000-28,000 EUR |
| Backend / API | Endpoints, business logic, DB | 20-30% | 16,000-24,000 EUR |
| Tests (unit, e2e) | Jest, Playwright, core coverage | 10-15% | 8,000-12,000 EUR |
| CI/CD & DevOps | Pipelines, environments, IaC | 8-12% | 6,500-9,500 EUR |
| Observability | Logs, monitoring, alerting | 4-8% | 3,500-6,500 EUR |
| Design system | Components, tokens, accessibility | 8-12% | 6,500-9,500 EUR |
| Security | Auth, headers, audit | 5-8% | 4,000-6,500 EUR |
Why Next.js and TypeScript in 2026
The stack choice isn't cosmetic: it drives perceived performance, SEO, speed of change and future hiring cost.
| Criterion | Next.js + TypeScript | Legacy SPA stack | Concrete benefit |
|---|---|---|---|
| Performance / SEO | Native SSR/SSG, Core Web Vitals | Client render, weak SEO | Better ranking, conversion |
| Type safety | Strict TypeScript | Untyped JS | Fewer production bugs |
| Speed of change | Reusable components | Duplication | Faster delivery |
| Ecosystem / hiring | Vast, 2026 standard | Shrinking | Talent available |
| 3-year cost of ownership | Controlled by tests | Growing debt | -20 to -40% TCO |
A tested and typed foundation costs a bit more to build but makes every future change predictable: it's the difference between an app you grow and an app you rewrite in two years.
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Mini case study
Sofiane, CTO of a SaaS scale-up in Paris, must replace a slow legacy SPA capped at a 55 Lighthouse score and expensive to maintain. We rebuild in Next.js + TypeScript, with Playwright on critical flows and full CI/CD, for 95,000 EUR in 5 months. The Lighthouse score jumps to 96, feature time-to-production drops from 9 to 3 days, and the monthly fix budget falls by roughly 40%. The investment pays back through regained velocity and speed-driven conversion.
FAQ
Why pay for tests the client never sees? Because they prevent regressions and make every deploy safe. Without tests, each change is a gamble; with them, the 3-year maintenance cost drops sharply.
Is Next.js fit for small apps? Yes: it scales from a small internal tool to a high-traffic platform on the same foundation. Hosting (often 200-800 EUR/month) is sized to real load.
Can an existing app be migrated gradually? Often yes, page by page or module by module, to avoid a risky big-bang. Discovery determines the least risky migration strategy.
Does TypeScript slow development? A little at the start, but it clearly accelerates once the app grows by reducing bugs and easing refactors.
What hosting budget should I plan? Plan 200 to 800 EUR/month on managed cloud depending on traffic and workloads, scalable upward for heavy load or compliance.
Let's scope your project. Describe your target app, expected traffic and an indicative budget: we'll propose a sized Next.js architecture. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.
Mohamed Bah
Fondateur, Kolonell
Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.
