Seeing some crazy prices being quoted here.
The core home user Vista product (the version that in 95% of cases is actually just what the user needs, nothing more, nothing less) should be priced at around the same as the WinXP Home Upgrade is £85 - £90
Slightly more advanced version which will cover the other 5% of home users should be priced around the WinXP Pro Upgrade price - £150 - £160
The "real" price of Windows has not really increased since the release of Windows 95 (inflation and assuming Retail Upgrades purchased for like-for-like versions).
Not bad for a monopoly - the real price of a product not really increasing over the past 12 years.