The word underpaid seems too friendly. In the case of the open source developers I know, they don't get any money
It seems to me that the current youth generation is less "giving" than previous ones. 70s , 80s and 90s where full of "sharing is caring" mantra. We had people like Stallman, a lot of "crackers" removing copy protection and people just sharing their stuff on an individual level (via edonkey, soulseek, imeem, etc). Same with software, I would never feel "underpaid" for software I release as open source. It's just some code I share, with some open license. If I keep building it, is because I enjoy it.
But now, everyone is driven by monetization so much. Maybe it's the fact that it had gotten more difficult to make ends meet, and everyone is looking for a way ti squeeze a cent.
I just miss those days.