I'm amused at all the highly-paid software engineers in this thread who legitimately feel entitled to their Silicon Valley pay-scale. The only reason you make more than the fellow laying your tile is because of supply and demand, not because you deserve it. If anything, he certainly works harder and longer and risks more health consequences than you.

If Facebook is offering less than the market price for that labor, then employees will go elsewhere. Otherwise, they're paying the "right" amount for workers in that market. There's no moral dimension to this question.