> That's assuming all sectors have become more efficient. Some, like construction, have become less efficient. And that's a big problem when it's relevant to necessities like housing.

Housing prices aren't going up because of construction costs alone. The biggest increase is from the cost of land. For that the cost of a house on top has become less and less relevant. If construction became really cheap, prices would still trend upwards since there's always some billionaire's money to be parked somewhere.

The biggest increase is from the cost of zoning making land artificially scarce. But construction costs layer on top of that because of the nature of it: Instead of being able to build 20 new housing units on a lot that currently only has one and enough land to add more without destroying the existing building, adding more is now restricted to a small strip of the downtown where the lots already each contain 10 housing units. Which effectively doubles your construction costs to add 20 housing units because you still have to build 20 housing units but now you have to destroy 10 in order to make space, and then do that twice to actually add 20.

Which is a disaster if construction also got twice as expensive.

> If construction became really cheap, prices would still trend upwards since there's always some billionaire's money to be parked somewhere.

If construction became really cheap and there wasn't an artificial limit on how much housing you could build on a given lot then there would be tons of cheap housing and billionaires wouldn't find it a useful place to park money because it would have lower returns than competing investments.