Windows 8 is the cheapest Windows yet
Microsoft just announced that the upgrade to Windows 8 Pro - available to users running Windows XP, Vista, or 7 - will cost a whopping $40. That's for upgrades downloaded from Windows.com, mind you, but that's the primary means by which Microsoft expects to sell upgrades. If you buy a boxed upgrade DVD in the store, it will cost you $70.
Note that Windows 8 Pro does not include Windows Media Center, but the Media Center pack will be offered as a free download.
This is a dramatic reduction in price for Windows; the "Pro" version usually retails for closer to $200, with upgrades north of $100. Microsoft admits this is a promotional price, set to expire on January 31st 2013, but I suspect most users will have either upgraded by then, or will simply wait until they buy a new PC to get Windows 8.
There's no word yet on how much manufacturers will have to pay to license Windows 8 Pro for their PCs, nor what Windows RT licenses will cost for those making ARM-based tablets. Given the agressive upgrade price, it's a safe bet that manufacturers will pay a lot less to load Windows on their products than they do today.