I completely don't get location-based pay. I provide you with some work, that's worth some amount of money. Why does my location change the value of my work? Do I suddenly become better if I move to SF? I get that some people have arguments for it, I just entirely disagree that any of them are valid. Whether I'm in a city that costs a lot to live in is no more the responsibility of my employer than whether I like to…
Salaries don't differ because of cost of living. They differ because of supply and demand. A software engineer in SF probably has a higher BATNA than one in Delhi. Not in every case, but in most cases. So the amount you'd need to pay her to accept is higher than the amount you'd need to pay the engineer in Delhi. You could decide you'll pay them both the same. Or you could decide you're not willing to pay SF salaries…
Why did you assume the gender of the software engineer?