The verdict in three sentences
The cost of a B2B platform does not stop at go-live: maintenance runs 15 to 20% of the build cost per year, typically 12,000 to 40,000 EUR. On top come EU hosting with CDN (200 to 800 EUR/month), security updates, and time-and-materials evolutions (600 to 800 EUR/day). Underbudgeting operations means letting the platform degrade from year one.
Anatomy of an annual budget
Maintenance is not passive insurance: it covers fixes, security, compatibility and a baseline of evolutions. Here is a typical 2026 split for a platform whose build cost 120,000 EUR.
| Line item | 2026 annual range | Share of budget |
|---|---|---|
| Corrective & preventive maintenance | 18,000-24,000 EUR | ~45% |
| EU hosting + CDN | 2,400-9,600 EUR | ~15% |
| Security updates | 4,000-8,000 EUR | ~12% |
| Monitoring & supervision | 1,800-4,000 EUR | ~7% |
| Time-and-materials evolutions | 8,000-20,000 EUR | ~21% |
| Indicative total | 34,000-65,000 EUR | 100% |
Fixed maintenance or time-and-materials?
Two models coexist. A fixed maintenance contract smooths spend and guarantees contractual responsiveness; time-and-materials bills actuals and suits unplanned evolutions. Most mid-market firms combine both: a fixed contract to keep operations running, T&M for new features.
| Criterion | Fixed maintenance | Time & materials |
|---|---|---|
| Budget predictability | High | Low |
| Day rate applied | 550-700 EUR | 600-800 EUR |
| SLA / guaranteed times | Yes | No |
| Ideal for | Keeping ops running | One-off evolutions |
| Commitment | 12 months | Per order |
The cost of downtime
A 99.9% availability SLA allows about 8.8 hours of downtime per year. For a B2B platform, every hour down costs dearly in lost orders and customer trust. This figure is what justifies monitoring.
| SLA level | Downtime/yr | Avg hourly revenue | Potential annual loss |
|---|---|---|---|
| 99.0% | ~87.6 h | 3,000 EUR | ~262,800 EUR |
| 99.5% | ~43.8 h | 3,000 EUR | ~131,400 EUR |
| 99.9% | ~8.8 h | 3,000 EUR | ~26,400 EUR |
| 99.95% | ~4.4 h | 3,000 EUR | ~13,200 EUR |
Mini case study
Claire, CFO of an industrial SME in Lyon, invested 120,000 EUR in her B2B platform. She budgets maintenance at 18% (21,600 EUR/year), plus 5,400 EUR of EU hosting and 12,000 EUR of T&M evolutions, roughly 39,000 EUR of annual operating cost. By moving from a 99.0% to a 99.9% SLA, she cuts her potential annual loss by about 236,000 EUR for a monitoring surcharge of 3,000 EUR: the decision is settled fast in the executive committee, and the platform stays secure and up to date.
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FAQ
Why is maintenance calculated as a percentage of the build?
Because the complexity to maintain is proportional to the complexity built. 15 to 20% of the build is the 2026 market range for a B2B platform.
Can you skip maintenance in year one?
No: it is the year most fixes and adjustments surface. Without maintenance, bugs pile up and security degrades.
Is EU hosting really necessary?
Yes for GDPR compliance and performance for European customers. Budget 200 to 800 EUR/month depending on traffic and CDN.
Fixed or T&M for evolutions?
Fixed for operational upkeep with an SLA, T&M for new features. The mix avoids paying for responsiveness you do not continuously need.
How do I budget a high SLA?
Compare the monitoring surcharge to your hourly revenue. Moving to 99.9% costs little against the tens of thousands of euros of avoided lost orders.
Let's scope your project. Tell us your platform's build cost and your hourly revenue: we price a tailored maintenance + hosting + SLA contract. 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.