If the sales are as bad as it would appear, I am not sure this is a good idea, but Microsoft are doing it anyway.
Apparently, the price MS have been charging for Windows 8 until the end of this month is a special offer. Starting on February 1st, the cheapest upgrade for Windows 8 (currently $39.99) will be $119.
http://www.theregister.co.uk/2013/01...counts_ending/
I really think Microsoft have lost their way recently. Raising the price of a product that isn't selling is unlikely to help sales.