There is also the fact that moving costs time and energy, and an engineer in the Bay Area will have a lot more options for employment if they stay in the Bay Ar

There is also the fact that moving costs time and energy, and an engineer in the Bay Area will have a lot more options for employment if they stay in the Bay Area- they can walk between interviews for large multinational tech companies in a lot of cases. Moving from a hub like that has the implicit cost that you may have to move back at some point to find work, or accept the lesser options and negotiating position.