Tom's Hardware has a good article on The Apple Mac Cost Misconception. As a recent mac user, this hits my heart because I've heard a lot of these misconceptions for years from my peers (and myself of course). Good to see it all laid out.
From the section on "I can build a mac pro for half the price":
The above is essentially a baseline Mac Pro replicated using the cheapest minimum required components to build. The difference? A negligible $5.67. Those who claim that they can build "the same" PC for half the price are at this point baseless.