There's also the issue of what happens to my money as a researcher. Is it paid to the company, or is someone holding it in escrow? What if it takes the developer months to respond, or they never do? Do they just get to keep my money indefinitely? What if the vendor pulls out of the scheme? What if I do a chargeback on the payment I made? Etc, etc

I wonder if a better model would be to make the platform pay to entry, but not the specific bugs? So you have to pay a fee to gain access to a platform like HackerOne, and if your signal:noise ratio gets too bad then your account gets revoked? That would make it feel like less of a gamble than having to pay for every individual bug - but still has the same problem that it's putting a big barrier in front of legitimate good-faith researchers.