Amazon has it for $125! It comes with two disks.. one with 32bit on it and one with 64bit on it. You can install windows on up to three machines total using either (or both) of these disks.
http://www.amazon.com/Microsoft-Windows-Premium-Upgrade-Family/dp/B002MV2MG0/ref=sr_1_1?ie=UTF8&qid=1288281641&sr=8-1While technically these are upgrades, I installed all three of mine on freshly formatted systems (one with a new hard drive) as new installs and it never asked me for the old disk, OEM number, etc... Apparantly sometimes it does, and sometimes it doesn't.. but even if it does there is a registry tweak you can make to make it work.
It's only home premium, but I firmly believe the 99% of people who purchase Ultimate never use the "Ultimate" functions anyway.
Enjoy!