HorizontIt's the decision that saves — or costs — the most money in the whole project: do you pay a monthly subscription for a ready-made tool (SaaS) or invest in a custom system built around the way you work? There's no universal answer, but there is an answer for your case. This guide gives it to you without the hype: where each option wins, the real three-year maths and a matrix to decide in five minutes.
The underlying difference (in one sentence)
With SaaS you rent a standard tool and you adapt to it. With custom software, the tool adapts to your process and the code is yours. Everything else — price, timescales, integrations — follows from that difference.
An honest comparison, point by point
| SaaS / subscription | Custom software | |
|---|---|---|
| Upfront cost | Low: you start paying little each month | Higher: there's a development investment |
| Cost over 3-5 years | Always rising: an indefinite per-user fee | Pays for itself in 1-3 years; then it's yours |
| Speed to start | Immediate: you sign up and use it | Weeks to the first useful module |
| Fit with your process | You adapt; whatever doesn't fit stays in spreadsheets | Built around how you work |
| Cost per user | Grows every time you hire someone | Zero: 5 or 50 users makes no difference |
| Integrations | Whichever the vendor decides | Banking, tax authority/VeriFactu, email, whatever you need |
| Ownership and lock-in | Stop paying and you lose it | Your own code, data and infrastructure |
| Maintenance | Included in the fee | A separate fee (optional, no tie-in) |
Notice that neither column wins on everything. SaaS wins on speed to start and upfront cost; custom wins on fit, ownership and long-term cost. Anyone who tells you one option is always better is selling you theirs.
The three-year maths (a realistic example)
Picture a team of 10 and a SaaS tool at €40 per user per month:
- SaaS: 10 × €40 × 36 months = 14.400 € over three years… and still climbing, with nothing of it yours.
- Custom: a working MVP at €4,000-9,000 plus optional maintenance. By year two or three you've matched the spend, and from then on the cost collapses.
The conclusion isn't "custom always works out cheaper" — if there are only two of you, custom may never pay for itself. The conclusion is that the number of users and the years of use are what tip the scales. The more of both, the more custom wins. You'll find the investment broken down by phase on our pricing page.
Decision matrix: which suits you?
Custom software suits you if…
- Your process is your own and no standard program covers it well (you end up with parallel spreadsheets).
- You pay for a lot of per-user licences that grow every year.
- You use three or four programs that don't talk to each other and you copy data by hand.
- You need to integrate banking, VeriFactu invoicing or AI-driven automation.
- You want the data and the code to be yours, without depending on a vendor.
Stick with SaaS (for now) if…
- A standard tool covers 90% of what you do.
- You need something working by tomorrow.
- Your process still changes every week and hasn't settled.
- There are only a few of you and the licence cost is manageable.
The third way: start with SaaS and move to custom
It isn't black and white. The smartest move is usually a hybrid one: you start with a cheap SaaS to validate the process, and when the standard tool starts holding you back, you build the module that hurts most to measure — not everything at once — and migrate that data. You reduce risk, spread the investment and keep what already works. It's exactly what we recommend to anyone whose process hasn't settled yet.
The expensive mistake: "it almost fits"
The costliest problem isn't choosing wrong, it's staying on a SaaS that "almost" fits. That word — "almost" — is paid for in hours: small manual workarounds, a spreadsheet here, a copy-paste there, every day, for every person on the team. Added up over a year, those hours usually cost more than the custom development that would have removed them. If this sounds familiar, work out how many hours a week go into gluing systems together: that's your real cost of SaaS.
Tell us about your process in a 30-minute call and we'll say frankly whether custom software pays off or whether a SaaS will do the job. No strings attached.
Let's talk about your case
Read on: how much custom software costs · CRM vs ERP: which one you need · real cases in production.