A new leaked screenshot of Windows 8 perhaps prematurely reveals the digital download cost of Windows 8 Pro. Revealed by Deskmodder, a screenshot depicting a page that allows you purchase a Windows 8 Pro product key lists a price of €59.99, with a further €14.99 if you wish to purchase a physical DVD on top of that.
Converting these prices to US dollars you get roughly $75 for the license, which could suggest a $69.99 standard price in standard pricing conventions, plus around US$20 for shipping out a Windows 8 DVD to you.
We already know that Microsoft will be offering Windows 8 Pro upgrades for just $39.99 until January 2013, that will allow you to upgrade any version of Windows as far back as Windows XP provided you have a previous valid license. ~$75 for the full version would be very cheap considering Windows 7 Ultimate cost $319.99; however we do know Microsoft is aiming to lower the barrier of entry at this stage to sell the OS.
This price could just be a promotional deal like with the upgrade, or it could be outright false as Microsoft haven't as yet made an official announcement, so we'll just have to wait and see.