Prefabs are, correct me if I'm wrong, made using current technologies, which are more expensive than just printing off a few walls, a base and all the other stuff. Also, the 3D printer is potentially much faster. In fact, scratch that, I am reasonably sure that it is much faster, and can, or will soon be able to, produce a similar quality product for less cost, and with less waste. Also, I suspect that you would be able to transport these printers in one or two large trucks from some nearby construction centres, with the trucks also going back to get the feedstock.

The internet of things stands to greatly increase the efficiency of the current logistics systems in place. I mean, they're shockingly bad. I was actually surprised by how inefficient they tend to be. And this whole paragraph is largely useless.