Officeworks has already commenced undercutting the market and is offering the Windows 8 Pro upgrade for $48.72.
While many of its competitors are offering the new boxed edition of the Windows 8 Pro upgrade to home users for approximately $58.00, and the full retail price for the upgrade is $69.99, Officeworks seems to be the current cut-price winner at $48.72.
If you're happy to download a copy from Microsoft rather than buying a DVD, then you can save a little more. If you have Windows 7, Vista or XP yoiu can download and install Windows 8 Pro for $39.99. If you bought your computer after the 1st of June 2012 the price drops to $14.99.
Note that these official Microsoft prices are all introductory prices valid until the end of January 2013.