The verdict in three sentences
Across 12 seats, a vertical SaaS suite costs 6,500 to 10,800 € per year — a 3-year TCO of 20,000 to 33,000 € while owning nothing. A custom build requires 38,000 to 70,000 € upfront plus 15-20 % annual maintenance, but the per-seat cost drops to zero. The break-even point sits between 28 and 34 months: beyond that, custom becomes structurally cheaper for a growing firm.
Breaking down TCO line by line
The classic trap is comparing a monthly subscription to a one-shot quote. Everything must be normalised over 36 months, migration and training included. 2026 order-of-magnitude figures for a 12-person Dublin firm:
| Cost line | Vertical SaaS (12 seats) | Custom build |
|---|---|---|
| Licence / initial build | 6,500-10,800 €/yr | 38,000-70,000 € one-shot |
| Annual maintenance | included | 15-20 % of build (6,000-14,000 €) |
| Data migration | 4,000-9,000 € (often extra) | 4,000-9,000 € |
| Training (2 days at 1,200 €/day) | 2,400 € | 2,400 € |
| Hosting / infra | included | 180-450 €/month |
| Cost per new seat | +45-75 €/month | 0 € |
The decisive line is the last one: each hire adds 540 to 900 €/yr to the SaaS bill, while custom absorbs growth with no extra licence cost.
Cumulative TCO: the break-even point
Adding every line together produces a curve where custom starts higher then gets caught up. Estimate for 12 seats, 6,000 € migration, 2,400 € training:
| Milestone | Vertical SaaS cumulative | Custom cumulative |
|---|---|---|
| Month 12 | 17,000-22,000 € | 48,000-82,000 € |
| Month 24 | 26,000-35,000 € | 56,000-96,000 € |
| Month 36 | 35,000-48,000 € | 64,000-110,000 € |
| Blended cost / seat / month | 81-111 € | 148-254 € then declining |
| Break-even | — | 28-34 months at +3 seats/yr |
Custom wins mainly if the firm expects to pass 18-20 staff over the horizon, because SaaS grows linearly with headcount.
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Mini case study
Sarah is a partner at a 12-person Dublin firm with a plan to reach 18 seats within three years. The vertical SaaS at 60 €/seat/month costs her 8,640 €/yr today, but 12,960 €/yr at 18 seats — roughly 33,000 € over 3 years. A custom build at 55,000 € plus 18 % maintenance runs to about 84,000 € over 3 years — pricier at the 36-month horizon. But as soon as she projects years 4 and 5 at 20+ seats, custom moves back ahead: her decision depends on her growth horizon, not the sticker price.
FAQ
Does TCO really include migration? Yes, and it is often forgotten: moving the client base, mission history and configuration costs 4,000 to 9,000 € whichever path you choose. SaaS vendors frequently bill this on top of the subscription.
At how many seats does custom pay off? As a 2026 order of magnitude, beyond 18-20 staff and over a horizon of 3 years or more, because the SaaS per-seat cost becomes the dominant line.
Is custom maintenance negotiable? Yes: 15 % covers fixes and security, 20 % includes regular feature evolution. Scope it in the contract to avoid change orders.
Can you mix both approaches? Frequently: custom core for production and the portal, SaaS bricks for payroll or document management. TCO is then compared module by module.
How do you de-risk the one-shot budget? Split into deliverable lots (production, billing, portal) with payment milestones, and keep a 10-15 % contingency.
Let's scope your project. Tell us your headcount, your growth horizon and your current tools: we model your 3-year TCO, SaaS vs custom, with a costed indicative budget. 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.
