[air7]

Higher salaries are not compensations for higher CoL but rather both are a result of more demand to live in a certain area (partially because of there being many jobs but that's unrealated).

If a company wants to attract talent in an area with a lot of competition it has to raise its salary offers. And rent goes up in the same way.

So no, it's fair (in some sense) to offer people different salaries based on their location (when work was on site) but that's part of the personal negotiations that take their other options (or lack there of) into account, but it's not some kind of automatic compensation you can demand or expect and with remote work its becoming more and more irrelevant.

[R0b0t1]

The issue is when the companies aren't trying to attract people. If the work can be done remotely they typically want to pay less based on local CoL.