I assume you missed the part about building 10 single-room buildings in a day for $5,000 each.
Well, the price is right, but people have been building modularly for a long time. Single room buildings don't really seem that challenging, especially since it is just a concrete box.
The Hilton Palacio Hotel in San Antonio was built in just 202 days, and that was 500 rooms, fully furnished, decorated and kitted (down to the bottle openers and coffee makers). And this was back in 1968.