The verdict in three sentences
At 20 users, a vertical SaaS (Pennylane, ACD, Cegid Loop) around 40 € per user per month costs about 96,000 € over five years, modules extra. A custom build is 90,000 € to build + 15,000 €/year maintenance = 165,000 € over five years, but you own the asset and get unlimited integrations. Custom tips in your favor above 25 users, with atypical workflows, or when you need an API into a key client's ERP.
Year-by-year TCO comparison
Total cost of ownership (TCO) is the only honest basis for the decision. Here is the projection for 20 users, 2026 order of magnitude.
| Year | Vertical SaaS (cumulative) | Custom (cumulative) |
|---|---|---|
| Year 1 | 19,200 € | 105,000 € |
| Year 2 | 38,400 € | 120,000 € |
| Year 3 | 57,600 € | 135,000 € |
| Year 4 | 76,800 € | 150,000 € |
| Year 5 | 96,000 € | 165,000 € |
| + modules / add-ons | 15,000 – 30,000 € | included |
Over five years at constant headcount, SaaS stays cheaper in raw cash. But the math changes the moment headcount grows: each new user costs 480 €/year in SaaS, versus 0 € of license in a custom build.
The tipping points that flip the math
Three factors push the balance toward ownership, regardless of the number of years.
| Factor | Tipping threshold | TCO impact |
|---|---|---|
| Number of users | > 25 users | 480 €/user/year avoided |
| Atypical workflows | 3+ non-standard processes | Modules unavailable in SaaS |
| Client ERP integrations | 1+ enterprise API | 5,000 – 15,000 €/connector in SaaS |
| Strategic data | High confidentiality | Full hosting control |
| Multi-entity / brand | Franchise, network | Licenses multiplied in SaaS |
With 30 users, SaaS climbs to 144,000 € over five years excluding modules, narrowing the gap with custom to under 25,000 € while leaving you with no owned asset.
Mini case study
Marc, a partner in a 28-person firm in Lyon, is undecided. On SaaS at 40 € per user per month he pays 13,440 €/year, i.e. 67,200 € over five years, plus 12,000 € in advanced billing modules. Total: 79,200 €. A custom build costs him 95,000 € to build + 60,000 € maintenance over five years = 155,000 €. The 76,000 € gap looks huge, but his firm targets 45 staff within four years: at that size SaaS exceeds 108,000 €/year and custom becomes the cheaper option from year 4, asset owned as a bonus.
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FAQ
Is SaaS always cheaper at the start?
Yes, almost always: no build to finance, live in a few weeks. Custom only pays off over a 4-5 year horizon or under strong constraints.
Where is the custom break-even?
Usually between year 3 and year 4 for a firm over 25 users. Below that, SaaS stays cheaper across the whole period.
Where should proprietary accounting software be hosted?
On OVHcloud or Scaleway in France for GDPR compliance and data sovereignty. Budget 1,500 to 4,000 €/year of managed hosting depending on load.
Can we migrate from SaaS to custom later?
Yes. Many firms start on SaaS then switch once headcount and workflows justify it. Budget 5,000 to 12,000 € for data migration.
Does custom really allow unlimited integrations?
Yes, that is its main edge: APIs to banks, client ERPs and internal tools with no per-connector fee, unlike SaaS which bills each integration.
Let's scope your project. Share your current and target headcount, your specific workflows and an indicative 5-year budget between 90,000 and 165,000 €. 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.
