Apple OS upgrades are becoming cheaper day by day to attract more customers, which might put pressure on Windows to reduce the rates of their platforms
http://www.notebookcheck.net/How-Mac-OS-upgrades-and-becoming-cheaper-and-Windows-more-expensive.76832.0.html
I think the title of the article was meant to be How Mac OS upgrades ARE becoming cheaper, and Windows more expensive and not How Mac OS upgrades and becoming cheaper, and Windows more expensive?
Now, for the uneducated fool like myself (and please correct me if I'm wrong), going from Windows 7 to Windows 8 seems like an complete OS upgrade. Going from OS X 10.6 Snow Leopard to OS X 10.7 Lion to OS X 10.8 Mountain Lion seems like an incremental upgrade - the type that Windows provide for free via Windows Updates! :)