You could also view it as a ~$100 discount on the Mac OS X tax, if it's only $400 more than equivalent Windows or Linux tablets. Apple laptops tend to be about $500 more than similarly equipped laptops from other manufacturers (my last Dell was $626 cheaper than an almost identically equipped MacBook Pro).
Of course, I don't know what Windows and Linux-based tablets are actually going to cost, so the Mac OS X tax may be more or less on tablets. I guess we'll see when the tablets start hitting the market in reasonable numbers.
I'm not entirely sure I see the use case for a tablet at any price...though I have a netbook, and like it, and have a Kindle, and like it (but the insane battery life is a primary factor for the Kindle; a tablet won't be able to come close). So, I may figure out uses for a tablet when they're more common.
I find that some people have an Aspergers-like view on laptops. If two laptops have the same processor, HD size and RAM, then they're identical.
But of course there are other important specs like the materials used in the construction. Alluminium is more expensive than plastic and far stronger and sturdier. A thinner laptop is also much more expensive. It requires thinner DVD drives and fans. Motherboard components need to be shrunk. Need to use smaller, more expensive capacitors. A smaller, more dense battery with the same capacity. The same core temperature with a much smaller thermal envelope. Minimalist design. None of this is trivial and adds significantly to the cost.
I agree that there is a premium placed on mac products, but I would guess you are overstating it. I'd be willing to bet that the difference in price lies in the RAM. Apple uses DDR3 while most other manufacturers use DDR2. If you look on Newegg, you will see that there is a substantial price difference in the two (at least at my last check).
