Companies know exactly what they pay to maintain an old system. Almost none of them know what it costs them to still have it.
The four components of real TCO
One: direct maintenance and licences — that one is on your invoices. Two: manual work around the system; if three people spend an hour a day re-typing data, that is over €18,000 a year at an average salary. Three: outages — an hour of a stopped warehouse in a manufacturing company costs €2,000–15,000. Four: missed opportunities, every time sales does not get a feature because “our system can't do that”.
When to modernise — and when not yet
The rule we use in audits: if annual TCO exceeds 35 % of the price of a new solution, modernisation pays for itself within three years. Below that line, isolate the system behind an API layer and replace it piece by piece — no downtime, strangler pattern.
The hidden fifth component: people leaving
The most expensive TCO item appears on no invoice — it is the people who quit because they fight a tool from the last decade every day. Hiring and onboarding one person costs €10,000–20,000; a senior who leaves, fed up with a slow system, takes the know-how with them. Once you fold turnover into TCO, the line for modernising moves sooner than maintenance alone suggests.
The risk that doesn't accrue — it explodes
An old system is not just expensive — it is fragile. It often runs on a version that no longer gets security patches, it is held together by one person who “knows where to kick it”, and the backup was last tested years ago. This risk does not show up gradually; it shows up all at once, at the worst possible moment. Module-by-module modernisation lowers it from the first month, not only at the end.
The first step does not cost six figures: a 48-hour audit with numbers tells you which side of the line you are on. The only thing worse than old technology is deciding without data.