If you were able to save a percentage of your income, then that percentage is going to result in a higher amount for the FAANG salary.
An example, is buying a house.. and rent pricing reflects purchase price.
If you buy and pay off a house, you have "spent" that salary in both locations. However, when you retire, you have property worth a LOT more in SV.
So while the "take home" pay, after expenses is the same with 150/400, the equity is massively different.
If you were able to save a percentage of your income, then that percentage is going to result in a higher amount for the FAANG salary.