ATI is selling off the remaining chips and selling the X1800XT in its 256MB incarnation at very attractive price. Fall-out chips are used for X1800 GTO cards.
The company is completely moving its high-end to the R580 and is about to launch the Radeon X1900 GT to take on Nvidia's Geforce 7900 GT.
ATI already dumped the Radeon X1800XL and replaced it with the Radeon X1900XT, so it won't be long before we see the last of those R520 chips. It had a rather short life cycle, not even a full six-months but, for ATI, the R580 is much-improved offering.
ATI finally listened to the voice of reason and lowered the price of the X1800 GTO to $/200. The card was too expensive to compete with Nvidia's 7600 GT chip. The new R580+ is still far, far away, at least till the end of summer. µ