Just because something cost X dollars to build doesn’t mean it has X dollars of economic value. Look at cars: you buy a car for 40K and a couple of years later it’s only worth 30K even if you don’t put any miles on it. There’s such an oversupply of houses now (many of which are not near any job centers) that no new ones need to be built for quite a while. They just don’t have much economic value.
