What about a system that allows requiring a fee to "open an issue" or "file a bug report". GitHub could add that to the issue creator pretty easily. And maybe there could be tiers. Free issue == no guarantees. $5000 issue == guaranteed fix.
What if there's a dispute about whether it's fixed or not, who decides who gets the keep the money?
Lack of a feature is considered a bug. This is often exacerbated by a similar commercial offering, that has the feature.
I used to get that crap, all the time, in my work.
These days, no one pays any attention to my work, which suits me just fine. I basically write for myself.
A lot of FOSS work is done as a labor of love, not a job. In order to make good on a promise to fix something for money, that means it's now a job. That may be OK for many FOSS projects, but it is completely incompatible with others.
One problem though is you’d need a strict definition of complete, and someone to arbitrate.
QA has value and is not a burden.
The perverse incentive would be to avoid fixing bugs or adding features because someone might add a bounty to it in the future, but that's limited by the possibility of a fork. Maybe limit UI for bounties to FOSS projects (that can be forked.)