One of the factors deterring many consumers from upgrading their PCs to Vista was the high price points for the new shiny operating system. The folks at Microsoft were finally let in on the secret, and decided to lower the price points of Vista substantially.
The new price points are staggered so as to encourage consumers to select the highest edition they can handle - don’t say we didn’t warn you that you might actually spend more money upgrading your machine to handle a higher edition of Vista than you’ll save on the software.