Readers wanted to know how those costs got so high and what is behind it. The details are complicated, but the answer is pretty straightforward: Everything is behind it. Material costs are going up, land costs are going up, labor costs are going up. Add that to all the regulatory hurdles and developer impact fees — which in California are about three times the national average — and it adds up to dubious distinctions like San Francisco being the second most expensive place to build in the world.

Not that this is all the fault of policy. Construction is one of the least productive industries, and despite all that’s happened with robots and computers, the building sector is about as efficient today as it was 50 years ago. To combat this, a number of developers are trying — with mixed success — to build modular housing that can be stacked like Legos, figuring that if they can move a large chunk of the construction process indoors to an assembly line, they can drastically lower the cost.

You can’t talk about costs without getting into politics. Environmental rules, union wages, fees that help fund schools: These are the sorts of priorities that any attempt to reduce construction costs will run into. But it’s a conversation that has to happen, regardless of what side of the political aisle you’re on.

The more it costs to build, the more subsidy it requires to make units affordable. The more subsidy it requires, the fewer people are served by it. In the end, building a building is building a building. Whether you’re building condos for profit or subsidized housing to advance social equity, the basic process is the same. The higher it costs to do it, the fewer you will get.

[Read more of Conor’s work here.]