I'm not sure exactly how fair it is to compare the Mac Pro on price to current PCs since no PCs are currently being sold with the Nehalem chips.
About a year ago, I did a full price comparison between the then Mac Pro 8-core and an extremely comparable 8-core PC build. At that time, the Mac Pro was about $800 less than what I would have built myself. Add on to that the fact that the Mac Pro comes with a 1-year warranty, the OS license, and I don't have to take the time to order everything and build it myself, and it was pretty clearly worth the price.
Now, as far as Apple's peripherals go such as their monitors and memory, etc. Never EVER buy them from Apple. Definitely, too expensive for what you get. While I personally think their computers are a good deal (especially if you factor in the fact that their OS and accompanying software is much more refined and stable than Vista is), I think Apple makes a killing however on their peripherals.