Microsoft did cut the price of Windows to get people to adopt it early on because they would be making so much money from Office.
Microsoft Word vs. WordPerfect, Excel vs. Quattro Pro and Lotus 1-2-3. These battles were won because of Windows and that cemented their position as industry leader.
Now that Microsoft is in a dominant position they don't cut the price of Windows as much, but to remain on top they do give the OEMs a very sweet per-unit deal they really can't refuse.