The verdict in three sentences
A documented ERP integration API, with webhooks and error handling, costs between 20,000 and 50,000 EUR in 2026 for a mid-market firm. The realistic timeline is 2 to 4 months, monitoring included. The ROI comes not from the API itself but from ending double data entry: often 20 hours per week recovered.
What makes up an integration API budget
Price depends on the number of flows to sync, the quality of the existing ERP's API and the required reliability level.
| Item | Content | 2026 estimate (EUR) |
|---|---|---|
| Framing + data mapping | Fields, transformation rules | 3,000 – 7,000 |
| Documented REST API | Endpoints, OpenAPI, versioning | 6,000 – 15,000 |
| Real-time webhooks | Event push, signatures | 3,000 – 8,000 |
| Error handling + retry | Queue, idempotency | 3,000 – 7,000 |
| Monitoring + alerting | Logs, dashboards, alerts | 2,000 – 6,000 |
| QA + documentation | Tests, integration guide | 3,000 – 7,000 |
| Total | 2 to 4 months | 20,000 – 50,000 |
A poorly designed API costs more in maintenance than in development: idempotency and retry are not optional once payments or stock are involved.
The ROI of ending double data entry
Double data entry is not just wasted time: it's a source of costly errors. Here is the order of magnitude for a 120-person mid-market firm.
| Metric | Before API | After API |
|---|---|---|
| Re-entry hours / week | 20 h | 1 h |
| Stock errors / month | 15 – 25 | 2 – 4 |
| Invoicing delay | 5 – 7 days | Real time |
| Monthly re-entry cost (loaded) | ~3,500 EUR | ~180 EUR |
| Cash-flow lag | High | Low |
At 3,500 EUR saved per month, a 35,000 EUR API pays back in about 10 months, excluding gains from avoided errors.
Mini case study
Sophie, IT director of a distribution mid-market firm in Dublin, wants to connect her ERP to her B2B store and her accounting tool. Quote: 34,000 EUR for a documented REST API, stock/order webhooks and monitoring, delivered in 3 months. Before, two clerks spent 20 h/week re-entering orders, i.e. ~3,500 EUR/month loaded cost. After, that drops to 1 h/week. The investment pays back in 10 months, and stock-outs from errors fall by 80%.
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FAQ
How much does an ERP integration API cost in 2026?
Between 20,000 and 50,000 EUR depending on the number of flows and the quality of the ERP's API. A two- or three-critical-flow scope usually lands around 30,000 – 35,000 EUR.
How long to go live?
Expect 2 to 4 months. Data mapping and QA often take longer than the development itself, especially with an older ERP.
Are webhooks essential?
For real time (stock, orders, payments), yes. Without webhooks you depend on scheduled syncs that create lag and errors. Budget 3,000 to 8,000 EUR for this piece.
How do you handle ERP outages?
With a queue, automatic retry and idempotency: no data is lost and nothing is processed twice. That's a 3,000 to 7,000 EUR item you should never cut.
What is the typical ROI?
Ending double data entry often means 20 h/week, i.e. ~3,500 EUR/month loaded cost for a mid-market firm. A 35,000 EUR API pays back in about ten months.
Let's scope your project. Tell us your ERP, the apps to connect and the priority flows, and we'll cost the API and its go-live timeline. 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.
