[londons_explore]

Yes, but I think their printer design could be improved.

I would go for the printer being far less weight by making the whole thing a cable truss and winch structure. That should cut the hardware cost in half or better, like the way a travelling circus tent can be assembled entirely without a crane, yet packs into a tiny box. The downside is you can no longer assume a rigid structure, so you need cameras and alignment marks for precise positioning - but you probably needed them anyway. You also can't make any accelerations above 1G, but that should be fine for housebuilding.

And obviously, their design only makes the walls, but I would want to do foundations, roof, insulation, plumbing and electricals all with the same machine.

[secabeen]

Yeah, getting plumbing and electrical as part of the print seems key. The current ICON system looks cool, but at the end, you have a concrete structure with no openings for these elements. Pictures of ICON buildings show electrical installed entirely with visible conduit, and protruding J-boxes, and don't show rooms with plumbing at all. I don't think many home-buyers would want a home without utilities embedded in the wall as in traditional construction.

[eightysixfour]

The hardware costs are minimal compared to other costs. It packs into a container.