I would not use Facebook and Amazon when comparing margins and profit. Both of these two companies aren't even in the same universe right now with Apple. Google is the only company that can play with Apple and Microsoft.
Last time I checked, Amazon posted in Q4 of 2012 around $90M (Million) in net income while Facebook did about $60M in Q1 of 2013 compared to Apple's $9.5B (Billion!!) in net income.
What drive me absolutely crazy is the fact that it would take Amazon/Facebook well over a decade to even come close to what Apple makes in three months.