I think one of the biggest costs can be training the workers (and then monitoring them to make sure they are doing it right for the first 10-20 assemblies). It would be neat if the engineer recorded himself building a one-off pilot build, moving to each section of the assembly line. Then each worker could wear HUD glasses with video set at semi-transparency or only have video on one eye (since they are becoming more mainstream and cheaper). Have a pause button mounted to a wrist-strap in case they aren't keeping up.
Each section of the assembly line trains in their section for 20 pieces, then they give the glasses to the next section (cut down on number of glasses needed).
* Any new trainees could be quickly taught what to do
* Any future owners would have a DVD that follows the machine, and not only know exactly how things go together, but it documents every piece needed to assemble (how many times do you buy a pin, and parts are missing that you don't even realize are missing, and the manuals aren't detailed enough for you to know any better)