Sure, given a dev in India and a dev in SF with the same skill set, then the one in India will be willing to work for less. But when you offer a SF salary in India, then you might get a much better dev.
So, theoretically, in case of remote work and a global pool of talent, it is a less optimal use of your dollars to adjust salaries to the cost of living (all other things being equal, e.g. skill set level, culture).