Wouldn't that be an excellent outcome for the person with the idea?
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)