You don't understand the issue at all. The "officially unlocked" 16G 3G in Europe costs 800 Euros. The subsidized ATT 16G 3G in the US costs $300.
The difference is that ATT pays Apple $400 per phone to keep the user price down to $300. ATT makes back the $400 it paid to apple on the users' behalf over the two years of the contract. The ATT phones are so much cheaper because ATT has bought them for you; ATT will get its money back over the two year period of the contract.
If you took out a two year loan from a bank to buy a phone for $400, and after paying back $200 you told the bank that you would like to borrow another $400 *and* have the bank forgive the $200 you still owe on the first loan, do you think they would go for that? Banks here do some dumb things, but I don't think that even they would be that dumb.
And the thing is, keeping in mind that ATT lent you $400 for your phone, they are being as reasonable as possible. If you have only had a contract for a year, they will partially subsidize your new phone with a new contract - you pay $300, they pay $200, and you get a new 3G-S phone for $500 rather than the list price of $700. Or, if you don't want a contract, you can also just buy a no-commitment phone for $700.
Finally, although the details on this aren't clear, it looks like some people with expensive plans are allowed to buy a new subsidized phone after one year - presumably because they paid enough to cover ATT's loan for the cost of the phone.
But the fact that some countries in Europe require iPhones to sold at the full 800 Euro price has nothing to do with the fact that people who bought iPhones in the US for $300 and a two year contract commitment don't understand why ATT won't let them out of the contract and buy them most of a new phone after only one year.
