Windows 8 Upgrades for $15 : Should they be Free?

If you buy a Windows 7 PC starting tomorrow, you can upgrade to Windows 8 for only fifteen dollars.  People who buy Windows 7 PCs will go live tomorrow and last through January 31, 2013.

PCs preinstalled with Windows 7 Home Basic, Home Premium, Professional, or Ultimate can be cheaply upgraded to Windows 8 Pro under the offer. To qualify, Windows 7 PCs must be purchased between June 2, 2012, and Jan. 31, 2013, and have a valid Windows 7 OEM Certificate of Authenticity and product key.

To order the cheap upgrade, buyers will have to register through the Microsoft site by February 28, 2013

In  a way I feel like it’s smart of Microsoft to offer the upgrade at a cheap price, but then when I think about it I wonder why they can’t offer a Windows 8 upgrade for free if anyone buys on through valid dates.  I would expect that by doing that they would get more sales rather than anger people by charging extra to upgrade to the new Win. 8 OS.   What do you think?  Was is smart of Microsoft to offer the 15 Dollar