My son is attending university in the UK and wants to buy an iPhone that he can use there for 9 months of the year and use here in US for 2-3 months of the year.   An unlocked iPhone 4S 16 GB on the Apple US site is $549+tax. The same unlocked phone on the Apple UK site is 449 pounds ($732).   Obviously the price difference is substantial, but does it make more sense for him to buy in UK since he will be there most of the time, or is an unlocked phone an unlocked...