You pay for everything you build - the more complexity you put into it the more that costs over time. Dependencies need to be updated, language/framework upgrades usually break something, new features/requirements introduce additional complexity and code to manage. Software just costs money every day - not a lot, our industry is much lower margin than, say, stamping sheets of metal into tools - but it still has operational costs beyond just the money to operate the hardware we run our products on.

I know that. This looks like some lib you update once a year/every new CVE, and it is compared to a lib from cloud vendor and also update once a year/every new CVE, which is why I asked what it costed YOU in this particular case.