The problem with the open source software is not that it is being restricted by monopolistic Micro$oft, but that it entails considerable transaction costs - main of which is steep learning curve, considerable knowledge of computer software operations, and the limited choice of applications. These transaction costs often outweigh the sticker price of the Micro$oft products.
I was thinking of switching to Linux long time ago, and I was even prepared to spend some time to acquire the necessary programming knowledge to accomplish that. However, had I done so, I would not be able to use certain crucial applications (such as SPSS) and I would have difficulties exchanging files with my work machine (which uses Windows OS) and my co-workers. A 100 or so bucks is a small price for avoiding such hassles.
Wojtek