The verdict in three sentences
To manage matters, time, billing and tax deadlines, a vertical SaaS costs 25 to 60 EUR per staff member per month and deploys in weeks. A custom tool (40,000 to 120,000 EUR) becomes worthwhile when per-seat licensing durably exceeds the amortised cost of owned software, generally beyond 15 to 25 staff. The real question is not the sticker price but the 5-year total cost, including licences, integration with your production suite and productivity gains.
Vertical SaaS vs custom: the 2026 comparison
| Criterion | Vertical SaaS | Custom build |
|---|---|---|
| Entry cost | 25 - 60 EUR/user/month | 40,000 - 120,000 EUR |
| Rollout time | 2 - 8 weeks | 4 - 8 months |
| Customisation | Limited to options | Total |
| Production-suite integration | Standard, sometimes paid | Bespoke |
| Code ownership | No | Yes |
| Cost at 20 staff/year | 6,000 - 14,400 EUR | Maintenance 12-18 % |
| Evolution | Vendor roadmap | Your priorities |
Cost per staff member and tipping point
Five-year projection, excluding productivity gains, as a 2026 order of magnitude.
| Firm size | SaaS at 45 EUR/user/month (5 yrs) | Custom 80,000 EUR + 15 %/yr |
|---|---|---|
| 8 staff | 21,600 EUR | 140,000 EUR |
| 15 staff | 40,500 EUR | 140,000 EUR |
| 25 staff | 67,500 EUR | 140,000 EUR |
| 40 staff | 108,000 EUR | 140,000 EUR |
| 60 staff | 162,000 EUR | 140,000 EUR |
The pure cost crossover happens around 50 to 60 staff, but firms often move to custom well before that, from 15 to 25 people, when specifics (deadline workflows, client portal, production integration) no longer fit a standard SaaS.
Mini case study
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Sophie, partner at a 22-person accounting firm in Bordeaux, paid 11,880 EUR/year for SaaS licences poorly integrated with her production suite, causing 6 hours of re-keying per week. A custom tool at 74,000 EUR, wired to production and a client portal, eliminated the re-keying: 312 hours saved per year, worth over 18,700 EUR, plus the retired licences. Full payback in about 3 years, with owned, evolvable code.
FAQ
At what size does custom become worthwhile? Usually from 15 to 25 staff, when annual licences pass 8,000 to 12,000 EUR and business specifics throttle productivity inside a standard SaaS.
Can a custom tool integrate with the accounting production suite? Yes, via API or connectors. Budget 8,000 to 25,000 EUR depending on how open the vendor is; some expose full APIs, others require gateways.
What is the timeline for a custom tool? Between 4 and 8 months depending on scope (time tracking, billing, tax deadlines, client portal). A first usable module can ship in 10 to 14 weeks.
How are tax deadlines handled in the tool? A workflow engine ties each matter to an obligations calendar (VAT, corporate tax, filings) with alerts and assignment. It is often the highest-value custom module.
What annual maintenance budget should I plan? Budget 12 to 18 % of the build cost, i.e. 5,000 to 20,000 EUR/year for a 40,000-120,000 EUR tool, covering regulatory updates and support.
Let's scope your project. Share your headcount, current production suite and target budget: we cost SaaS vs custom and the tipping point. 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.
