You say programmer or AI researcher? The details number I don't know, many programmer exit China not just for high pay, but for avoid the crazy totalitarian gov, and exit China to other country is not an easy thing, many of them are failed.

But in the other hand, programmer in China is a good job, they can earn enough money (compare to other job), many of them are enjoy their life and don't want to exit China just for more money(even thought they know they will lead by a fool gov).