For a PC of the same price, you could have a machine with twice the power. It's like buying a Lamborghini, it's not really that much better than a $100,000 car, but it costs $250,000 because they can and because they have a reputation.
They have resistance to most but not all viruses (I work in IT, I've seen a few Macs killed by viruses), and when they do get a virus, it's incredibly hard to get rid of, since there is less anti-virus tools, and I'm generally worse with Macs.
Windows gets hit by a few more problems, but it usually gets back up and running a lot easier and cheaper. Unlike Mac, where you may be forced to take it to an "Apple Genius" and pay through the ying-yang... again.
Windows supports more applications, and is far more open and free, where as Mac is controlled and very totalitarian. Might not bother granny McApple who only need to check her email once a week, but it annoys me to no end. Also, I find the UI disorienting, being a Window's user, although that is personal preference.
A lot of it is personal preference, but I find I can save money and avoid headaches by sticking with PC.