How do you think Costco gets a fresh banana from South America to your local store for 20 cents?
By taking a cut of the sale price of the banana as margin to cover it's costs and profits, and then passing the rest down the supply chain to Some Banana Company?
Flipping your question around, why does the banana cost 20 cents and not 5 cents? Where do you think the upward pressure on the price comes from?
Facebook treats its employees pretty well too. Not sure if that really means anything in this discussion.