XP Home or Pro aren't cheap, even if you buy OEM your looking at around ?60 and ?100. Those Vista prices leaked were for retail i would imagine?
At the end of the day, when XP seems old and even more insecure and featureless, if Vista was a really big step (which it wont be for a long while - other than visually) I would just go over to an alternative OS which could cost, well... nothing at all.
And for pity sake, I thought when XP Home and Pro looked to draw together Win 2K and 9x/ME I thought MS were on a mission to simplify their products, now Vista comes in six vaguely different editions - very helpful.
I appreciate the "starter" edition is for low power PCs, and that is primarily to compete with open source software and existing Windows versions but the other editions are only going to complicate matters further for consumers.