It does not seem wise to charge a fixed one time fee of a few hundred bucks when the customer then uses the library for years in their own products. Is it still common to charge per installed CPU/core? How do you then deal with cloud systems where that number always changes and may even be difficult to determine? What about charging "per end user"? In general, can libraries also be charged on an ongoing basis like a SaaS (x EUR per month or year), i.e. do customers accept that?
I've offered maintenance and support packages but when the software works beyond the initial warranty, customers usually don't order them. I could turn the library into an API and charge for that but that's not always what the customer wants.
Any ideas on how to maximize my revenues here?