Have 3-4 story house going up in my neighborhood on a narrow lot. Builder told me it was ~500K in material and labour for the building.
I was floored.
If building a new building on free land costs 500K then no property collapse is likely to make housing affordable.
We need to ask why it is so expensive to build a building in the first place.
It doesn't cost that for the materials. New houses today are made of cardboard. I've watched them put up a lot of them around me since I moved in. They're nothing but wooden frames with some pressboard over them, plastic insulation and vinyl siding (with stone on the front side). And these are $600-$800k homes.
It's the land and the army of lawyers that costs money. The permits take lots of time to negotiate and come with lots of conditions and fees to the developer.