what people do is that they get these iphones on contract, claim them as stolen and get a new one in insurance while the 'stolen' one is shipped back to pakistan via a relative. This way a $100/$200 iphone is sold for 50k and plus. The stolen phone is blocked in the US but no worries for the seller because he will be selling the phone in pakistan. This is how 99% of the iphones, imates and HTCs are sold here.
If everyone was so pious then you would not need to unlock these iphones because the seller would get a factory unlocked phone from apple. Its just plain common sense!
How do I know this? Someone I know used to do exactly this but as someone correctly said haram ki kamai mein barkat nahi hotee,,,,the person lost everything he earned and more in another venture!