Comment by ecshafer

I think that more than physics the bottleneck for this is political (at least in the US). All of the local large projects around me are expensive because of massive amounts of red tape (environmental studies, zoning, planning), and political patronage systems. After the kick backs, political donations, promises to only work 8 hours a day, only use union labor, hire x police officers for y hours in overtime security positions a month, use xyz contractor etc. a small cost seems to be the actual labor and materials. Hell these robots if they work will be made illlegal.