bug bounties compete among themselves. Honest researchers will be busy finding some mobile game bugs for $700 a pop or improving security at google or yahoo for up to $10k instead of helping your company save from a 9 figure bug because you only offer $100
This is the minimal bounty.
They do state "Rewards over the minimum are at our discretion, but we will pay significantly more for particularly serious issues, i.e. that the identified issue could put a significant number of users at risk of severe damage, monetary or otherwise."
What they consider significant is anyone's guess. Given the stakes, even a 10000% increase would still be underwhelming for a high impact bug.