Depending on the exchange you get it can work out much cheaper, im pretty sure if you get an unlocked one then its just the sim card in and away, but i think the Apple stores only sell them linked to AT&T
for eg Basic I Pad is 499 Dolars at 1.30 to the pound its 384 Quid, Im lucky i still have 700 quids worth of dollars that i bought at 1.98 the the pound.