Google makes $1m per average employee; it's not hard to believe they can make many times that on an AI researcher.

I don't know if you're wrong, but you're certainly not alone. If you read history, or you're old enough, you'll know that we've already had at least two AI winters (mid 70s to early 80s and early 90s to early 00s), depending on how you count them, and the hype around machine learning is almost word-for-word the same as the hype around expert systems was last time around. This bubble is ripe for bursting.

I think that there are 3 or 4 companies who would have happily paid that for say Alex Krizhevsky ("Alex Net") a few years ago, and it's pretty clear that would have paid off (it certainly has for Google).