I think it ultimately comes down to the decisions of the marginal worker. Most people are not indifferent to where they live. In the Bay Area, as long as the

I think it ultimately comes down to the decisions of the marginal worker. Most people are not indifferent to where they live. In the Bay Area, as long as the tech industry continues to grow at a rate faster than new local graduates, you have to pay people enough to convince them to migrate. Since the cost of living is much higher, they will demand more to move. In senior roles, many employees will put more of a premium on being able to afford a decent house and be less willing to live with roommates or in a tiny apartment, and so you see the rates for senior employees are much higher in the Bay Area.