Is custom software cheaper than per-seat SaaS in the long run?
For most teams of 10 or more using a tool costing £5–80/seat/month, a custom replacement becomes cheaper within 12–24 months. You pay once for a build (shared across a founding cohort), then a flat annual fee that never grows with headcount. Every new hire on a SaaS pushes your bill up; every new user on your own system costs nothing extra.
Why per-seat SaaS costs compound
Every hire adds to the bill. Every annual review adds to the bill. There is no finish line.
Per-seat SaaS pricing has two compounding factors most finance teams under-model: headcount growth and annual price increases. A tool at £20/seat/month for 20 users costs £4,800/year today. At 10% annual price growth and a team that doubles in three years, the same tool costs over £15,000/year by year five — and you still own nothing at the end.
When custom software beats per-seat SaaS
More than 10 users + more than £100/month total = custom likely wins by year two.
The crossover depends on three inputs: current annual SaaS cost, build cost (shared across co-funders), and headcount growth rate. For field-service, ATS, and scheduling tools at £30–90/seat, break-even for a 20-user team is typically year one or early year two. For cheaper tools at £5–10/seat, it takes a larger team or longer horizon — but the direction is the same.
Related questions
For tools under £10/seat/month, you typically need 50+ users or a 5-year horizon. For tools at £30–90/seat, even a 10–15 user team can justify the build within two years.
Sources
- Retool 2026 State of Internal Tools: ~35% of organisations have replaced a SaaS; ~78% plan more
- Zylo 2026 SaaS Management Index: ~51% of SaaS licences unused
- Rollout IT build and running-cost estimates
See what your SaaS spend looks like with a flat annual fee.
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