The verdict in three sentences
In 2026, application maintenance (ADM/TMA) runs at 8% to 18% of the build cost per year, i.e. a retainer of €1,200 to €4,500/month for a mid-size app. A single fix ticket costs €350 to €600, and a critical SLA (< 4 h) adds around 30% to the bill. For an Amsterdam product manager, the right model depends on the pace of change: time-and-materials for living products, retainer for stability, per-ticket for minimal upkeep.
The three contract models compared
| Criterion | Time & materials | Monthly retainer | Per ticket |
|---|---|---|---|
| Billing basis | €550-700/day | €1,200-4,500/mo | €350-600/ticket |
| Budget predictability | low | high | medium |
| Responsiveness | high | SLA-backed | variable |
| Ideal volume | > 4 days/mo | 2-6 days/mo | < 2 days/mo |
| Enhancements included | yes | defined scope | no |
| Commitment | flexible | 6-12 months | none |
| On-call | optional | often included | no |
The 2026 maintenance line items
| Item | 2026 range | Basis |
|---|---|---|
| Maintenance retainer | €1,200 – 4,500/mo | monthly |
| Fix ticket | €350 – 600 | per unit |
| Enhancement day rate | €550 – 700 | per day |
| Monitoring + on-call | €400/month | monthly |
| Critical SLA < 4 h | +30% | surcharge |
| Security updates | included/quarterly | per contract |
| Managed hosting | €250 – 800/mo | monthly |
Simple rule: an app built for €50,000 justifies maintenance of €4,000 to €9,000/year (8-18%), adjusted for criticality.
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Lars, product manager at a 35-person e-health SME in Amsterdam, runs a web app built for €60,000. He's torn between time-and-materials and a retainer. On T&M he uses ~3 days/month at €620 = €1,860/month. He negotiates a retainer at €2,200/month including 3.5 days, monitoring, on-call and quarterly security updates. Over the year: retainer €26,400 vs T&M €22,320 + on-call €4,800 = €27,120. The retainer is slightly cheaper and adds the SLA — decision made for the retainer.
FAQ
How much is maintenance per year? Budget 8% to 18% of the annual build cost. A €50,000 app = €4,000 to €9,000/year of maintenance.
T&M or retainer? T&M suits more than 4 days/month of activity; below that, retainer or per-ticket are cheaper and more predictable.
What does a < 4 h SLA add? A guarantee that critical incidents are handled fast, for about +30%. Essential for a revenue-generating app.
Is monitoring included? Rarely by default. Budget €400/month for monitoring + on-call, often folded into the monthly retainer.
What does a fix ticket cover? Fixing an isolated bug, excluding new features. Price €350 to €600 by complexity; above 2 tickets/month, a retainer pays off.
Let's scope your project. Tell us your app's build cost, its criticality and your monthly change volume: we'll propose the most cost-effective maintenance model. 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.
