It looks like Dori Smith has been firing up Calculator.app recently because she shares some interesting figures with us. She takes the full retail price of Tiger ($129) and assumes that people who want to upgrade to the new OS may not have the latest and greatest hardware. Why not upgrade your hardware as well?
Won't that cost a lot more? Perhaps in days of yore, however there is a pretty little thing called the Mac mini in Apple's product matrix now. Therefore if you buy a Mac mini on Friday, or after, you get Tiger and a new machine for $499, and since you were going to get Tiger anyway the mini really only costs you $370.
I like that math!