[nikster]

Not doing this again now, but in my experience over the past few years the "Apple tax" on notebooks based on specs alone was about $100 - $200.

Apple doesn't sell cheap laptops but when you compare a $800 machine to a $1200 Mac, I dare say that many of the components in the $800 PC will be inferior, CPU, screen, etc. Not even mentioning the chassis where nobody can touch the unibody design of the Macs.

Apple makes premium stuff that comes with premium components - high end PCs which also come with premium components usually cost just as much, or just a tad less.

For the Mac Pro, it's probably a similar situation - you can probably make a cheap junk PC with the same CPU and as much HD space for much less, but if you use high quality components you'll be right up there fairly quickly.

As for tablets - Gruber's argumentation is way more conclusive, sorry.