Do you have to pay for some C++/C# libraries?

Question

I have heard that some libraries of these programming languages require you to pay for them. I have not found any proof of that, but could anyone tell me if it is actually true or false?

A friend of mine told me that, and now it makes me doubt.

Answer 1

I mean, anybody can write a library, righ? Though, charging for it’s got to be rare, as anyone that uses said library now has to deal with license usage of the proprietary software inside of their own. It wouldn’t work practically in my opinion.
That’s my guesses, anyway.