that is b/c apple is a mature company with mature products. Facebook hasn't even begun to reach their potential. Revenue streams are developing and open to new development much easier than at Apple. Although the numbers are high, the sales paradigm is going to completely change over the next few years....hope you join the ride up :)
FB has no products on their own to sell. Ad revenue will start go down with budget cuts and fiscal cliff. You can not beat AMZN or WMT selling products. Internet sales tax is on its way. So FB has no advantage. 12 year old kids using social network are not going to pay a single cent.