With all due respect you're wrong on many levels.
First of all no, nostr devs aren't paid as much as you think and yes a lot of us are working for free with am expectation of making money later.
Second, "build something close source and sell your startup" is a horrible mindset. There is almost never a reason to build something closed source. Closed source code is a temporary pandemic we're in the midsts of dealing with.
And finally Satoshi didn't work for free. Satoshi has (rightfully) earned several BTC by mining Bitcoin at the start