Here is an example of a very elegant and well executed design from FF. Keep in mind that the roof assembly is an option.
$20,000 for the kit. I would say if you are frugal, you could do one for $35,000
Now let's work this backwards, what are you willing to give up from this image, in order to bring the kit in at $8000-10,000? (8,000 for kit, + 3-5,000 for dead subie + 2,000 for odds and ends= $15,000)
I really am curious to see what comes of all this. My point is that few, if any, of the designs are cognizant of how minimalistic this design has to be. Forget drawing it on a napkin, it might have to BE the napkin!