The verdict in three sentences
SharePoint/M365 is cheaper to enter if you already hold the licences, but adapting it to specific processes stays limited and locks you into Microsoft. A custom extranet requires EUR 30,000 to 70,000 upfront but adapts fully, with no per-user licence and no vendor lock-in. The right choice depends on three factors: the specificity of your processes, your 5-year TCO horizon and your adoption requirement for external users.
Head-to-head comparison of the two approaches
SharePoint excels when your needs match the Microsoft standard and your users are already in the M365 ecosystem. Custom takes the lead as soon as processes fall outside the box, external user experience matters, or you want to own your roadmap without depending on a vendor.
| Criterion | Custom extranet | SharePoint / M365 |
|---|---|---|
| Upfront cost | EUR 30,000 - 70,000 | EUR 15,000 - 40,000 |
| Per-user licence | None | ~EUR 10 - 23/month/user |
| Customization | Full | Limited to M365 frame |
| External adoption | High (dedicated UX) | Medium |
| Vendor lock-in | None | Strong |
| Time to launch | 10 - 18 weeks | 4 - 10 weeks |
The 5-year TCO, the deciding factor
Total cost over 5 years often reverses the initial intuition. A SharePoint solution looks economical, but per-external-user licences and integration accumulate. Custom amortises its upfront cost and adds no per-seat charge.
| Item (5 years, 40 external users) | Custom | SharePoint / M365 |
|---|---|---|
| Upfront / integration | EUR 50,000 | EUR 28,000 |
| 5-year licences (40 users) | 0 | ~EUR 36,000 |
| Maintenance / evolutions | EUR 25,000 | EUR 15,000 |
| 5-year hosting | EUR 18,000 | included in M365 |
| 5-year TCO | EUR 93,000 | EUR 79,000 |
| Ownership + flexibility | Full | Limited |
Mini case study
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Laurent, IT director at a 600-employee industrial mid-cap, must open an extranet to 45 external partners. The SharePoint option means 45 external M365 licences at about EUR 20/month, or EUR 10,800/year, plus EUR 28,000 of integration: EUR 82,000 over 5 years. The custom option costs EUR 50,000 of development, with no per-user licence, plus EUR 43,000 of maintenance and hosting: EUR 93,000 over 5 years. The EUR 11,000 gap is small against full flexibility, no lock-in and higher external adoption. Laurent chooses custom for the non-standard processes and control of his roadmap.
FAQ
When is SharePoint the best choice? When your needs match the Microsoft standard, your users are already on M365 and the number of external users stays low. Integration costs EUR 15,000 to 40,000 and ships in 4 to 10 weeks.
When should you prefer custom? As soon as your processes are specific, external user experience is strategic, or you want to avoid vendor lock-in. Budget EUR 30,000 to 70,000 for full flexibility.
Does the per-external-user cost really weigh in? Yes. At ~EUR 10-23/month per external M365 user, 40 users represent EUR 5,000 to 11,000/year, or EUR 25,000 to 55,000 over 5 years, a line item absent from custom.
What does vendor lock-in mean in practice? Dependence on Microsoft's pricing, roadmap and limits. Migrating off SharePoint is costly; custom leaves you owning the code and the data.
Can you combine both? Yes: keep M365 for internal collaboration and a custom extranet for external users. This is often the best adoption/cost compromise for a mid-cap.
Let's scope your project. Share the number of external users, the specificity of your processes and your horizon (3 or 5 years): we cost the TCO of both options to decide. 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.
