The $7 cost is substantially lower for the manufactures buying these things at scale. That would apply to outlets and work boxes, too, but I'm assuming the reta

The $7 cost is substantially lower for the manufactures buying these things at scale. That would apply to outlets and work boxes, too, but I'm assuming the retail / wholesale difference is much higher with the mobile home parts. I'm also going to guess that these are much faster to install that proper outlets and work boxes. I've never seen one of these things get built but I'd guess the ability to quickly throw up drywall and then be about to float these outlets wherever need be (similar to old work boxes), without needing to put boxes on studs and drywall around them is a considerable time savings. They may also have tooling that makes making those single wire connections much faster/reliable than you'd be able to attempt to do at home.