I really, really fail to understand how this is not a super-expensive laptop, essentially? Is it considerably smaller/faster than an ultrabook? I'll grant that

I really, really fail to understand how this is not a super-expensive laptop, essentially? Is it considerably smaller/faster than an ultrabook? I'll grant that this is an interesting attempt at converging two devices, but such attempts ultimately succeed or fail based on how well they can replace either device. Would this thing replace your laptop? Your tablet?