Bug bounties, on average, have a signal:noise ratio that is horrible. I advocate for the programs completely, but they require a lot of planning in order to prevent them from becoming overwhelming. I personally know security engineers at Google and Facebook whose full time job is sorting through nonsense bug bounty reports.
What Tom said about people in Eurasia wanting to cash in on bug bounties is spot on. If you start a bug bounty program, expect to get a deluge of nonsense reports for bullshit like having the Trace HTTP method allowed on an API endpoint. For every one valid report, three - five will be bullshit. Of those that do not reproduce, half will be incomprehensible, and the other half will blatantly ignore the program guidelines or be low effort spam ("content spoofing"). If you offer a cash reward, expect the ratio of valid to invalid to be closer to 1 in 10.
It's a numbers game for these people. The security research industry is bifurcated between rare, sophisticated and highly paid freelancers who do it mostly for passion outside of their day jobs, and opportunistic amateurs who couldn't write a curl command.
From there it's pretty easy to see that "vulnerability spam" would be a thing.
>For every valid report they get, they get 3 that aren't valid.
Because taking the time to write and to submit an invalid report is a total waste of the reporter's time. Reports aren't the type of thing that someone will accidentally say "oh this is a severe vulnerability! here's some cash" even though the researcher has submitted bullshit.
So can you talk about "3 that aren't valid" for every valid report? Who makes these? Weird, obscure cranks, of the type who in other industries would be churning out perpetual motion devices? I would expect 80%+ of vulnerability reports to be serious and real - quite different from what you just wrote.