Well, many open source developers are quite content with making their software freely accessible without expectation of monetary gain. In fact some are strongly opposed to it (see uBlock Origin maintainer). And that’s ok too!

> made more money in hours than many free software

You’re sad that free software didn’t make money ?

Well that's not quite fair, it was expressly sold and they weren't.

If you can't make $40 off an open-source project in years, you are probably deliberately avoiding accepting money.

Probably the weirdest case to study right now is Dwarf Fortress? Did they hit a million yet?