> The last contractor we hired was for firmware and an issue we had, we needed someone with Rockchip experience and someone who could work on it full time.

"Full time" for $1000!

And it was an "issue with Rockchip", which sounds exactly like a problem that could be easily specified but impossible to predict how many hours it would take to fix.

GP seems like a rant from someone abusing a fixed price worker.

I do freelance embedded systems development. I do fixed bid work because I prefer it that way.

If I bid $2,000 to produce something, I either produce it for $2,000 or I say (hopefully within the first day) "sorry, I underbid this. I need to re-quote you, or you can have your down payment back." I've "eaten" quite a few underbids and only once returned a down payment and ended the job because the buyer kept increasing the scope.

OP's not "abusing a fixed price worker," he's holding them to what they agreed to do.