It was recently posted here that MKE has unlocked iPhones available. Looking at them, they have an unlocked 8GB iPhone for $645 -- this is the 'wholesale' price mind you -- compared to the $399 price at the Apple store.
Given that you have to sell this phone for a profit to someone else, it is silly to pay a 60+% premium over retail for unlocking.
I contacted MKE about the unlock process, who handles it, what about the warranty etc. and they refused to give any info, saying only that it would work world-wide and that they didn't recommend trying to get it fixed by Apple ('It is customer's responsibility to make sure Apple warranty is still in effect' they say.)
This is suprising from a supplier as generally reliable as MKE.
Anyone can buy an iPhone at retail and unlock it, thereby screwing up the original warranty. Instructions to do it are all over the Internet. And you can resell those unlocked phones too ... but based on the ones I've seen moving, you can expect to get $500-550.00 if you guarantee your work. Which is way under MKE's 'wholesale' price for the same thing.
The demand for unlocked iPhones all but dictates that as soon as Apple can legally do so (ie. as soon as whatever contract they have with AT&T can be gotten out from under) they will put an unlocked iPhone on the market. Maybe worth the wait?