OSX Mountain Lion cost $20.00 for a full version. Windows 7 cost upwards of $600.00 for a full version (Depending on which one you get). One of the main reasons for a Mac's cost is because of the proprietary hardware (Since they switched to Intel processors, the price has come down a little bit). When it comes to reliability, My Mac has 'NEVER' crashed on me. Windows has crashed more times than I can count. Mac is more secure than windows. There are some viruses that are starting to pop up for Macs, but there are still not nearly as many as with Windows.
I will say it again - Nothing beats a Mac ...
Damn, dude, I don't know where you're buying your copies of Windows, but W7 Ultimate is around $199. I just looked. Upgrades are cheaper. Of course it all depends on who it is purchased from. Sure, it ain't the $20 you tout for OSX. mac users beware, the virus makers ARE coming after y'all now. BTW, I worked on a mac desktop. It didn't look very "proprietary". It really didn't look any different than a PC. Of course, one can't just switch out to a newer, better video card without paying out the ass for it, unlike the PC platform.