They can always change their multipliers if they think the employees they're hiring there are getting paid more than they're worth relative to other locations. And lots of companies mostly just shrug rather than getting into a bidding war with FAANG in particular.
I mean Bay Area puts you near the big tech companies which is an interesting talent pool; their knowledge, experience and connections will have value beyond the skills needed for their day job.
Employees aren't interchangeable cogs. It's funny how HN will complain about outsourcing and offshoring as doomed endeavors when they imagine their own jobs going to someone in a lower cost of living location. Any company that fires an expensive employee to replace them with a cheaper employee in a different location is making a huge mistake! Employees aren't interchangeable cogs!
Then as soon as the roles are reversed we're supposed to believe that the people in the more expensive location are easily replaceable. Any company that pays people differently is making a huge mistake! Employees are interchangeable cogs!