If I were to look up salaries for those positions in bay area, they would be equal to those in rural Montana? If that's the argument you are making, I have no data to disprove it, so I would have to believe you, but it doesn't seem very likely.

That is not argument I am making. The difference in salary is in negotiation power, not in need, as shown by people who earn less while living at same location. Need is the same for janitor and programmers, however programmer have other employment opportunities and is more scarce resource.