Sony set the price at $600 because cost reductions would soon ensure that they were breaking even and they'd turn a profit before their initial price reduction (18 months later if it follows the standard Playstation pattern). Lowering the price in Q3 (to $400) would mean that Sony is reducing the price of their console at least 6 to 9 months earlier than they anticipated and would be returning to taking large losses on the production of the console.
No matter what Sony does at this point in time it will be a gamble; a price reduction will represent a large quantity of money on reasonable odds, and not producing a price reduction represents a tiny ammount of money on longer odds. Even a price reduction of $200 to $300 does not ensure success of the platform and 12 months after they produce the price reduction they could be forced to make this decision again.
