You do realize that a normal copy of Windows XP Home is $199 for full, $99 for upgrade but you can get a 3pack OEM for $264 right?
The problem with that, at least as I understand it (someone please correct me if I'm wrong), is that the OEM license is only good for a single installation (installation = unique hardware combination). If you upgrade your entire computer, or upgrade "too many components", you have to pay the Microsoft tax again because the OEM copy you have already paid for once cannot be validated against your new hardware.
I've been using the same XP license since XP was released, and within that time period I've done about 4 complete system rebuilds. I'm not at all interested in buying the same OS 3 extra times simply because I like to keep a current computer.
I like the idea of a lower priced family pack - big business gets a break on their per-copy licensing, why shouldn't the home user? I normally loathe Apple's business practices, but in this case it sounds like they have the right idea. Microsoft should follow their lead and make their OS more attractive to the multi-computer homes out there, which I am sure there are more of these days.