These salaries are supposedly tied to the cost of labor in various markets, and we're a large enough company that they do a lot of surveys of economic condition

These salaries are supposedly tied to the cost of labor in various markets, and we're a large enough company that they do a lot of surveys of economic conditions, what competitors are paying, etc. to set salary bands. But the cost of the sort of technical labor we're talking about here might vary more between SF and other markets than the general cost of labor.