The verdict in three sentences
A custom connector between ERP, CRM and billing costs between 10,000 and 40,000 EUR (ex. VAT) in 2026, over a 5-to-10-week timeline. The critical point is not moving the data but handling errors and logging every exchange to guarantee reliability. Against an iPaaS at 500-3,000 EUR/month, custom becomes profitable as soon as volumes or field-mapping rules grow heavy, removing up to 40% of double entry.
How much a connector costs in 2026
The budget depends on the number of systems, sync frequency and field-mapping complexity. Here are the 2026 ranges in France.
| Scope | Timeline | Budget (ex. VAT) | Double entry avoided |
|---|---|---|---|
| ERP ↔ CRM (2 systems) | 3-5 weeks | 10,000-16,000 EUR | 20-30% |
| CRM ↔ billing | 4-6 weeks | 14,000-22,000 EUR | 25-35% |
| ERP + CRM + billing (3 systems) | 6-8 weeks | 22,000-32,000 EUR | 35-40% |
| Multi-system + advanced mapping | 8-10 weeks | 30,000-40,000 EUR | 40%+ |
A robust connector always includes logging (traceability of exchanges) and a retry queue on failure, otherwise synchronization becomes unmanageable.
iPaaS or custom dedicated API
iPaaS excels at standard, well-documented flows. A dedicated API is required when sync reliability is critical and systems are old or specific.
| Criterion | iPaaS | Custom dedicated API |
|---|---|---|
| Setup cost | 3,000-10,000 EUR | 10,000-40,000 EUR |
| Recurring cost | 500-3,000 EUR/month | 300-900 EUR/month (maintenance) |
| Error handling | Standard | Custom (retry queue) |
| Old / specific systems | Limited | Adapted |
| Real-time frequency | Variable | Guaranteed |
| Cost over 24 months | High | Controlled |
Over 24 months, an iPaaS at 1,500 EUR/month represents 36,000 EUR: beyond that threshold, a dedicated API often becomes the most economical and reliable option.
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Mini case study
Karim, IT director of an industrial SME in Marseille (60 employees), runs a disconnected ERP, CRM and billing tool. His teams re-key each order two to three times: 25 h/week at a loaded cost of 35 EUR/h, i.e. 3,500 EUR/month. He invests 28,000 EUR (ex. VAT) in a three-system connector (7-week timeline) plus 600 EUR/month of maintenance. Double entry falls by 40%: 10 h/week recovered, i.e. 1,400 EUR/month saved; net of maintenance, 800 EUR/month net gain. Payback in ~35 months on time alone, but reliability also removes billing discrepancies, valued at 12,000 EUR/year of avoided errors.
FAQ
Do we have to change our existing software? No. A connector plugs into the APIs of your current tools (ERP, CRM, billing). You keep the existing stack and move data between them.
What happens if a sync fails? A well-designed connector logs the failure, alerts, and automatically replays via a retry queue. That is precisely what distinguishes custom from a simple script.
iPaaS or custom: how to decide? Compare total cost over 24 months. Beyond 1,500 EUR/month of iPaaS, a dedicated API is often cheaper and more reliable, especially with legacy systems.
How long to connect three systems? Count on 6 to 8 weeks for ERP + CRM + billing, including field mapping and failure-retry testing.
What concrete gain to expect? Up to 40% of double entry removed and the end of billing discrepancies between systems, often valued in thousands of euros per year.
Let's scope your project. Specify your systems (ERP, CRM, billing), their age and monthly order volume, with an indicative budget of 10,000 to 40,000 EUR (ex. VAT). 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.
