The verdict in three sentences
Extending your ERP is the right move when your processes match the vendor's standard and you want to build on an existing base. A custom platform wins when a differentiating process justifies owning the IP, or when the ERP module plus its integration cost nearly as much as custom without the flexibility. Between the two, a hybrid path (ERP for back-office, custom platform for the core) is often the best fit for a mid-market firm.
Costing the two paths
2026 order of magnitude, mid-market, EUR:
| Item | ERP extension | Custom platform |
|---|---|---|
| Upfront cost | 40,000-120,000 EUR (module + integration) | 60,000-150,000 EUR one-off |
| Additional ERP licenses | 15-40 EUR/user/month | 0 |
| Maintenance | included or 18-22 %/year | 15-25 %/year of build |
| Timeline | 3-6 months | 4-9 months |
| IP ownership | vendor | you |
| Scalability | bounded by ERP | in your control |
The switch criteria
Five criteria decide. Each leans toward integration or custom:
| Criterion | Leans ERP | Leans custom platform |
|---|---|---|
| Process fit | > 80 % covered | < 60 % covered |
| Speed of delivery | priority | secondary |
| IP ownership | non-strategic | strategic |
| Scalability / volumes | moderate | high / atypical |
| 5-year TCO | ERP cheaper | custom cheaper |
Rule of thumb: ERP fit > 80 % -> integration; fit < 60 % on a key process -> custom; in between -> hybrid.
When each option wins
ERP integration wins for cross-functional areas (accounting, procurement, HR) where reinventing the wheel makes no sense. The custom platform wins on the process that makes your difference: complex product configuration, proprietary pricing logic, specific field orchestration. The economic tipping point appears when ERP module + integration + licenses over 5 years exceeds the custom build + maintenance.
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| Scenario | ERP extension / 5 years | Custom platform / 5 years |
|---|---|---|
| 30 users, standard process | 40,000 + 27,000 licenses + 40,000 maint. = 107,000 EUR | 90,000 + 90,000 maint. = 180,000 EUR |
| 80 users, differentiating process | 110,000 + 144,000 licenses + 99,000 maint. = 353,000 EUR | 130,000 + 130,000 maint. = 260,000 EUR |
At 30 users on standard process, ERP wins comfortably; at 80 users on a differentiator, custom takes the lead.
Mini case study
Marc is operations director of a 180-staff industrial mid-market firm in Strasbourg, 80 users on the future tool. His ERP covers accounting and procurement well, but his custom product configurator (the heart of his competitiveness) is only 45 % covered. The ERP extension is quoted at 353,000 EUR over 5 years, with a constrained configurator. He chooses hybrid: keep the ERP for back-office and have a custom platform built for the configurator, at 130,000 EUR + maintenance. Outcome: IP owned, exact configurator, and about 90,000 EUR saved over 5 years versus the contorted all-ERP route.
FAQ
When is ERP extension clearly the right choice? When the vendor covers over 80 % of your processes without heavy custom development, and speed matters most. You build on a base your teams already master.
Does custom really take longer? Generally yes: 4 to 9 months vs 3 to 6 for an extension. But a poorly scoped ERP extension can drift just as much, if not more.
Can ERP and a custom platform coexist? Yes, that's the recommended hybrid path for many mid-market firms: an API between ERP and platform, each on its own turf. It often yields the best TCO.
How do I avoid paying for integration twice? Map the IS and define the ERP/platform flows at the scoping stage. A clear integration architecture avoids costly duplication.
At what volume does custom become worthwhile? Often beyond 50-70 users on a differentiating process, but the trigger remains the 5-year TCO crossing, not a fixed threshold.
Let's scope your project. Describe your current ERP, the coverage rate of your key processes and your volumes: we'll cost integration, custom and a hybrid scenario. 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.
