Not to sound STUPID or anything but I was wondering if anyone knows the reason that unlocked phones cost so much more than a carrier locked phone. It would seem a unlocked phone would cost less as the carrier (or distributor) has to do something to the phone to make it locked. I bought three AT&T 520 Go phones (that can be used on the prepaid network or the post paid AT&T network) for the price one unlocked 520 would cost. As I am on AT&T it did not matter; but I am considering changing to T-Mobile. They would not unlock my 820 until my plan was over, but would unlock the 520's after three months. ?????????????????