And in practice, it also "buys" you all of the other bug fixes and releases from helping to fund the developer. So while the bug itself might only take a day, the infrastructure around being in a position to do that takes much more time.
I was about to comment that most customers might expect more support than a bugfix for a $100k support contract, then I remembered my last few interactions with enterprise software vendors.
ETAs and individual bounties, I think, are different in a subtle way. ETAs require a strong organziation that can deliver such things. Piecemeal support to fix one bug does not.
Also, I've seen companies cut larger checks for sillier things with minimal conditions, so...