After a bunch of regulation, now, the "papers" cost more than materials to build, and most of the area is zoned as eg farming area, even though there has never been any farming there. Of course, prices have gone up A LOT, there is a lot of NIMBYism, by people who already build their house, and don't want another one next to it, and young people are basically fucked.
We might disagree, but in places with available land (and there are many), the only thing that stands between housing and non-millionaire people are (local) governments and regulations.