I was so satisfied with XP that I never even gave Vista a moment's look back in the day. Now, I know how critical people were of Vista so a question for the crowd:
Is the current discontent with W8 of a similar magnitude? more? less?
I was a late adopter of W7 too, moving to it barely 11 months ago - no regrets either, though I still think XP was, for it's time, better. When I picked up 7, W8 was on the verge of release but I had a bad feeling about 8 so decided better late than never with 7.
It wouldn't surprise me if W7 is priced higher than W8 simply because it's a better seller - people are willing to pay more since it delivers a better result for them and that 8 is lower priced simply in an attempt to make some kind of return in the hope's it will gain popularity and stick. Normally I'm not so quick to finger 'market forces' to explain pricing but in this case I suspect the reality of the products is driving the discrepancy.
M$'s stated objective of a 'unified cross-platform/device computing experience' may prove to have been be any unnecessary design constraint for them. It well may have tied their hands at critical junctures in the design design process - say, by sacrificing the main thrust of improving overall usability and performance for business and gaming in an effort to make it more tablet/smart phone/touchy/app-ish. We'll see...