Cool stuff
Nice concept - but renderings are the easy part. To hit that weight it's going to have to be a fiberglass - foam sandwich I would think, but that brings with some interesting manufacturing challenges and expensive tooling. I'll call it at $15 to $20 k per unit if made in Europe and shipped to USA.
The part I find curious is putting the spare tire in the bed. That rubber stink would be powerfully unpleasant if it was closed up on a hot day, and if you changed out a bad tire I wouldn't want the road dirt in my bed afterwards - and getting it in/out would be a chore on a humid day.