Hence the idea of prevailing wage, and paying somehow above that.
This of course creates an avenue to game the system, because prevailing wage for basically any work in SF or NYC is likely higher than on average over the entire US. You can undercut local markets a bit by bringing in smart people from abroad, and paying them less than they would make in SF or NYC if hired as locals, but more that the country-wide average.
(Smart, hard-working, educated people from underprivileged places get a chance of having a better life while working to improve the US economy! What's not to like?)