MacOS was a successful attempt to improve on Xerox's work. Windows was an unsuccessful attempt to copy MacOS.
The base machine usually costs 2 to 3 times as much for the same stuff
See my earlier laptop comparison.
Need more RAM? You can't buy the standard sticks, you need the parity stuff for $100s more - and so on.
The extra 2 GB for my iMac was standard laptop RAM from NewEgg. Only the Mac Pros need special RAM, and that's because they're Xeon, and all Xeons need this RAM. The only difference is that Apple requires a quality heat spreader (easily available from non-Apple sources).
Plus Mac software tends to cost more.
Have you compared the price of iWork and MS Office? have you compared the upgrade price of the OS itself, especially if you're upgrading multiple machines?
As for the virus and malware argument, the real issue is that the coders dont bother with Macs because nobody uses them. . . that's hardly a real advantage.
It's pretty big. In fact, it's been more than doubling recently. Plus, OS X being UNIX gives them the UNIX developers.
I used Macs since the first one, but not as my main machine. I've used Windows since the unbearable 80s editions. There is now no comparison: Going to the Mac as my main machine was a major relief in every way.