The only way it's going to be cheaper is if you're going to buy a used copy off somebody. Which I guess isn't that bad of a plan, but I don't see a lot of people selling their copies of Windows 2000 on the used market.
You'll pry my copy of Windows 2000 out of my cold dead hands.
I don't think there's much worth upgrading from 2000 to XP for right now. I'll have to upgrade from 2000 eventually, but I'll be sure to bitch like all the 98 guys when that time comes.