I sort of wish Apple, Amazon, Google, Microsoft and Facebook all contribute $200K each and say hey can you now make Mold MIT or BSD.
( I hope more US companies are opened to truly remote )
*in the US.
In my country, those salaries are completely unheard of.
I live in the UK and dev salaries are maybe half of the US, but people don't leave in droves because there are other factors - family, friends, quality of life, effort of moving your life across continents, etc.
Look at Sidekiq for inspiration on how to charge for open source.