Since Windows 8 was made available, you could grab the upgrade to Windows 8 Pro download for just $39.99 and the retail box version for $69.99.  The last day for this promotion is January 31st and after that prices go way up.

Prices starting in February:

• The Windows 8 Pro upgrade edition will be available online and at retail for $199.99 MSRP (U.S.).
• The Windows 8 upgrade edition will be available online and at retail for $119.99 MSRP (U.S.).
• The Windows 8 Pro Pack will cost $99.99 MSRP (U.S.).
• The Windows 8 Media Center Pack will cost $9.99 MSRP (U.S.).

I grabbed the $39 deal and was happy paying that price.  If you were thinking about upgrading, now is a good time.

More info at the Windows blog.

http://blogs.windows.com/windows/b/bloggingwindows/archive/2013/01/18/update-on-windows-8-pricing.aspx