The bounty idea is a good one, but again, I think it will rapidly become a race to the bottom on price. As soon as the bounty gets to the point where someone in e.g., Eastern Europe thinks it's good money, they'll bid on it even though a dev in SF thinks it's pocket change. I'll bet dollars to doughnuts that in a lot of cases it will happen as soon as the bounty hits $100.
One to get around this problem is to focus on only doing the same kind of work and getting better at doing it quickly so it becomes profitable to you, or doing it in a more Productized Service fashion. But that's a solution to a different problem, not what the OP was asking about.
I think this is the disconnect for me when reading this question. If the question is "where do I find good ideas for my personal tinkering projects" that's one thing, but if you're looking for profitable startup ideas it's not about the engineering - it's about testing quickly and validating the business so the development piece can be much less important (unless of course the business is software tooling)
They do more than just tech problems though, and the solver doesn't really maintain ownership
It's finding folks with a problem and some money that is the challenge. But if you figure it out you're gonna be in a great spot!
I'm curious if people posting things they NEED would be more functional, along with a bounty. Other people who also want it can contribute to the bounty. Anyone can work on the idea's and the bounty is awarded to whoever solves it first/best. (I think you would need some sort of oversight to make sure the bounty is awarded to the rightful solution).
"$1,500 - An API that lets me send send snail mail by posting a PDF and address to an endpoint"
Maybe it slowly gets up to $4,000 with 15 other people contributing to the bounty. That's finally high enough that someone solves it, posts it, collects the bounty, and already has 16 customers.