The verdict in three sentences
A custom REST API budgets at €8,000 to €20,000 in 2026, and each ERP connector (SAP, Sage, Odoo) adds €12,000 to €35,000 depending on synchronization depth. The real trap isn't the initial build but error handling, retries and annual maintenance, which cost 15-20% of the build every year. A sharp IT director budgets integration by integration, using middleware to avoid a point-to-point spaghetti mess.
What each integration brick costs in 2026
Cost depends on the exchange type (read-only vs bidirectional), volume and criticality. Here are the 2026 orders of magnitude seen on the market.
| Brick type | Build cost (€) | Timeline | Maintenance/yr |
|---|---|---|---|
| Custom REST API (documented) | 8,000 – 20,000 | 3-6 wks | 15% |
| SAP ERP connector | 20,000 – 35,000 | 6-12 wks | 18% |
| Sage / Cegid connector | 12,000 – 22,000 | 4-8 wks | 15% |
| Odoo connector | 10,000 – 18,000 | 3-6 wks | 15% |
| Middleware / iPaaS (subscription) | 300 – 1,500 /mo | 2-4 wks | included |
| Error handling + retry + monitoring | +15% of lot | — | — |
The "error handling" line is too often skipped: without automatic retries and alerting, a sync failing overnight creates stock or billing gaps that cost far more than the 15% saved.
Point-to-point or middleware: the real trade-off
When connecting 2 systems, point-to-point is enough. Beyond 3-4 systems, iPaaS (Make, self-hosted n8n, or in-house middleware) pays off by centralizing mapping, logs and retries.
| Number of integrations | Recommended approach | Estimated year-1 cost |
|---|---|---|
| 1 to 2 | Custom point-to-point | €10,000 – 30,000 |
| 3 to 5 | Middleware / iPaaS | €25,000 – 55,000 |
| 6+ | Dedicated integration bus | €55,000 and up |
| Critical real-time | Webhooks + queue | +20% |
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Mini case study
Marc, IT director of a 90-employee industrial SME in Lyon, wants to connect his production-tracking app to SAP (stock), Sage (accounting) and HubSpot (sales). Point-to-point: SAP connector €28,000, Sage €16,000, HubSpot €9,000, i.e. €53,000 plus 15-18% maintenance (~€8,500/yr). Using an iPaaS middleware at €600/month (€7,200/yr), the build drops to €38,000 because mapping is shared. Over 3 years, the middleware option costs ~€59,600 vs ~€78,500 point-to-point: nearly €19,000 saved and unified supervision.
FAQ
Custom API or the vendor's standard API? If the ERP already exposes a clean, stable API, use it (30-50% saving). A custom API is justified when the vendor exposes nothing or imposes quotas that are too low.
What's the real annual maintenance cost? Budget 15-20% of build cost per year: vendor-side API updates, fixes, adapting to new fields. On a €50,000 lot, that's €7,500-10,000/yr.
How long for a first ERP integration? From 4 to 12 weeks depending on the ERP and depth: SAP is longest (6-12 wks), Odoo fastest (3-6 wks).
Does real-time cost much more? Yes, budget +20% to move from a nightly batch sync to real-time via webhooks and a queue, due to the robustness and monitoring required.
Can the budget be spread out? Yes: we deliver the most critical integration first (often billing or stock), then the others in lots, smoothing cash flow over 6-12 months.
Let's scope your project. Tell us which systems to connect (ERP, CRM, billing), volume and real-time needs: we price each integration plus the middleware option. 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.
