I'd say mostly the reasons are non technical. There are a lot of amateur house builders that only build their own house. For them, building a house is a one off

I'd say mostly the reasons are non technical. There are a lot of amateur house builders that only build their own house. For them, building a house is a one off project. There is no scaling. You build the house and you are done. For big real estate developers, this is different. However, they have to deal with building codes, NIMBY's, and local contractors, building permits, and the occasional bit of bribes, corruption, nepotism, etc. that is ever associated with large real estate projects. There are a lot of people getting rich from the status quo. So, standardizing practices is challenging and every project is bespoke and different. And as the article actually suggests, even larger developers don't actually build that many houses either. So, the gains from economies of scale aren't that high for them either. And they in any case have to adapt to local situations in every project. That being said, prefab housing components are very much a thing these days. And with laminated wood, CNC cutting machines, there is not a lot you cannot construct pretty quickly. Also, it's kind of insane that e.g. a large camper van can be built in a very short amount of time (hours?) and is actually very suitable for living in. And yet we don't have a similarly efficient way of producing housing units. And of course plenty of people end up living in trailers that can't afford normal housing. And some of those aren't necessarily that bad even and they can be pretty roomy and comfortable. I don't think it's a technical problem. If it was, it would long have been a solved problem. Society simply does not allow people to do cheap and efficient things here but forces them to buy housing at extremely high prices. Otherwise, people would do the obvious thing of getting some old trailer, container or other form of cheap shelter and use it. It's not that hard technically to build something nice that provides a decent level of comfort and shelter. Nor is it very expensive. But it's simply not allowed to do that in a lot of places. Silicon Valley doesn't have a housing problem but a legislation problem. The same is true for Berlin where I live. Plenty of land here. They could build millions of houses, apartments, etc. here. Nice ones even. But it's not allowed.