Looks like not only are X800 XT's and Geforce 6800 Ultra's totally impossible to get your hands on, they are also pretty overpriced as well.
"The cards are virtually impossible to get in the US retail market, driving prices to new record levels... If you eyes are set on ATI's X800 XT Platinum Edition, get ready to pay for your graphic card about the same as for a mid-level PC."
If you are lucky enough to get hold of an ATI's X800 XT Platinum Edition, get ready to pay $600 to $900 for the sucker! Similarly, if your quest to obtain an Nvidia's Geforce 6800 is fulfilled, expect to pay something like $600 to $850 even when on backorder.