Most companies don't do bounties at all (and arguably they shouldn't). The idea that the companies that do are going to 2-3-4x pay the same bounty on a bug collision is unrealistic.
The "fair" thing here is probably to split the bounty among the discoverers, but that's not going to happen either.
The "fair" thing here is probably to split the bounty among the discoverers, but that's not going to happen either.