The fast downfall of the iPhone value can be explained simply: AT&T will subsidize the phone, attracting new customers. This is a standard practice for the American operator.
According to AT&T, such a scheme would allow the company a profit only in 2010. AT&T - the largest GSM-operator of the country - has signed with Apple a multiyear partnership agreement.
It worths to be mentioned that many observers had expected such a subsidy at the time of the first iPhone debut. How much it will cost in the overseas markets and what conditions of subsidy are planned – is not known so far.