In my experience.

The brain mostly follow the money and that inflates the salary for everyone in that area.

The very talented individuals who stay "home" get pretty much the same pay the individual Whould in an inflated area, but the individuals peers don't.

I think the inflation which happens in pretty much every large city with a thriving tech/startup environment, is largely due to the fact that lage groups of highly skilled and talented people gather and then that super salary becomes "normal" and then the rest wants an even salary. Lowering the tops pay is a no go as that salary they can get literally in any geographic location. Then the only thing left is base pay has to go up.

Just my guess.