Apple recently started selling unlocked versions of the iPhone 4 in the U.S. However, if an Apple retail store’s unlocked iPhone 4 stock runs low, the store can unlock an AT&T model at point of sale and charge the full price for the device ($649 and $749 for 16GB and 32GB, respectively).
AT&T customers had always been able to purchase contract-free iPhone 4 handsets, but the devices were stilled tied to AT&T’s network (i.e. they wouldn’t work on T-Mobile’s GSM network, or any others worldwide). Now, for the same price as a contract-free handset, GSM users can purchase the iPhone unlocked and use it on any network they please. Currently, the iPhone 4 doesn’t support T-Mobile’s 3G network, which is probably the only downside in owning an unlocked Apple smartphone in the U.S.
So, if you’re concerned about low stock of unlocked iPhones at your local Apple store, just ask them to unlock an AT&T SKU iPhone for you.