A $40K salary in Alabama might very well give you a higher standard of living than $80K in NYC or Silicon Valley, where housing and other necessities are very expensive (and income taxes are probably higher).
That's true, but he mentioned "$120k in Silicon Valley", which leads to believe the $80k applies to "places with a lower cost of living than Silicon Valley". I've looked at the numbers before and the standard of living evens out, depending on your priorities. If I live in San Francisco, I have a much shorter commute than my current 30-minute one-way drive from the suburbs - however, we'd have to double or triple our rent to maintain the same size apartment.
