Interesting. That does seem to be the general trend: 7800GT > X800XL, X1800XT > 7800GTX ... Once more people start buying X1800XL's, it would be interesting to see some overclocking results.
Regarding prices: cards will always cost more and be overpriced around their launch. The 7800's have had a couple of months for the prices to settle down. The ATI's have nowhere to go but down in price.
If I were buying a card right now, I'd probably get the 7800GT, or if I could stretch my budget, the GTX. In a few months, who knows...