Windows 8 Pro upgrade: $40
 

So, I guess Apple set a trend three years ago when it announced the $29 pricing for Snow Leopard (insert patent joke here). Microsoft has just announced the upgrade pricing for Windows 8 Pro - and it's good. Every Windows XP, Vista, and 7 install, no matter the version, is eligible for an upgrade to Windows 8 Pro (download version) for just $39.99. The fine print: this offer only runs until January 31, 2013.

http://osnews.com/story/26143/Windows_8_Pro_upgrade_40