I've been trying to get all upgrades, but it's really hard to lose money now. So betting max is no longer at least 10%, even after buying all max bet upgrades. I think either the xp upgrades should always activate at max bet, or there should be a final max bet upgrade that removes the limit on the max bet.
After you get to a million dollars, you unlock another max bet upgrade that got you covered until the billion dollars (the end of the game). Or maybe you're already at the billion dollars stage? In which case, yes the final "max bet" upgrade only covers until 2.5 billion dollars. I will add some more max bet upgrades.