Here's another wacky choice: Kay suggests the family will want add Blu-ray capability (which, it's true, is not currently supported by OS X) to the desktop system in year four. He budgets $95 for a Lite-On internal drive for the PC and $300 for an external Sony Blu-ray drive for the Mac. Never mind that, as they've chosen the extremely expandable Mac Pro, they could easily upgrade the computer with that same internal Blu-ray drive (presuming, of course, that four years from now, Apple's added Blu-ray support to OS X—if not, that Sony player won't be much more useful anyway). Knock off another $205.

But let's look at this from the other side for a moment: what's been left out of the costs of owning a PC? Well, how about security? Malware is a pretty common sight on Windows PCs and you won't find any expert recommending you run your machine without virus protection. But most virus protection costs a certain amount per year: HP, for example, includes 15 months of Norton Internet Security for free, but that'll leave the family out in the cold just over a year in—they'll have to spend another $60 to $80 to cover them for the whole five year period. And that's just for one of the two computers. Not much, but it adds up.