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.