It really is apples to oranges. Facebook paid a lot, but they paid in overpriced Facebook stock so maybe it balances out. Apple will be paying cash for a business that will probably pay for itself in just a few years via earnings.
Was slide to unlock invented by Google, or did Eric Schmidt take the invention from an Apple BOD meeting and give it to Google before it was patented?
Just because Google had it before the patent was filed does not mean that they invented it.