It sort of isn’t though, because it gives the wrong impression to people who look at things through a financial lens.

There’s no accrued compound interest: if you leave a piece of “indebted” software alone, you don’t pay any “interest”.

Conversely, a small amount of tech debt can actually cost huge amount… but only if you make many changes at a high rate.

That’s why I prefer the “worn tools” or “sand in the gears” analogies because they provide the right financial mental model.

An unlubricated, worn out piece of industrial machinery costs you nothing… unless you try to make things with it.

You can take this analogy quite far: sharp and lubricated but outdated machinery may work “just fine”, but you won’t be able to attract the top talent used to working with modern 5-axis CnC tools instead of having to manually turn cranks like a savage.