IMO, assuming everyone is WFH, Location based pay should only be considered within a same
timezone and in same
country.
Even if market rate price for developers in India was same as SF, to maintain its "output/$ per employee", the salary may differ.
For instance, a company whose main operations are happening in PST, engineers whose main hours are offset 13h30min are less valuable to the company than those with 0h0min offset.
Sending a PR for review or reviewing a PR from someone with more than 8h time zone difference usually means you have to wait a full day of turnaround time.
Now within a same time zone but different country (or even states in the US), the differences diminish but there are still local labor laws and taxes that affect what the ratio of "what the employee provides" vs "what it costs the employer"
So at the moment, people living in SF and [some remote town in the middle of california with fiber internet] should be paid the same, but, people in TX should not. (This only applies to 100% WFH companies whose majority of workforce is all in California)