It is partly a fixed cost versus variable cost argument, although these guys don't express it that way. (And I realize that fixed isn't really "fixed.") If you

It is partly a fixed cost versus variable cost argument, although these guys don't express it that way. (And I realize that fixed isn't really "fixed.") If you can't afford decent housing, adequate healthcare, and a good education for your kids, of course more money will buy you happiness. And in the US, the income at which you can afford those three ... is high and increasing fast.