If HP and Dell bought up 5600+ chips at higher prices, then they would indeed have an inventory problem which would explain why they are still charging the old prices for the high-end chips.
The Duke of URL, AMD can cut prices from one day to the next. But they can´t build a fab in a day. Customers (I´m talking large customers here) know that AMD has to price competitively to move their products. That´s why they worry about their capacity, not prices. If customers can´t buy AMD products, the best prices in the world mean nothing to them.