I think this is entirely about AMD rebranding their line to make more money.
Midrange cards being up priced one more tier and they are changing the 6770 to the 6870 series to justify what may be a 100 dollar price increase. I can see the 6870 being priced at $259-299 and people thinking its a good deal because the naming indicates better performance than the last generation but at the same time the pricing is lower and they think they are getting a better value. This allows cayman pro and xt to be priced at 399 and 499 respectively.
This allows AMD to increase its margins and will help them make big money for once. I can imagine AMD felt they price their last series too low and hence the card selling more than MSRP, so they want to raise the price of their whole lineup.
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