I don't think this computes. Modern 'efficient' industrial design can absolutely fail at efficiency. I have lived in spartan, utilitarian apartments that you could tell were built without any regards for efficient use of living space, and ended up wasting huge swaths of their floor area to interior corridors, winding tunnels between rooms, random walled off mystery areas and overall such poor planning that I'm sure despite their builder trying to save every buck, ended up costing more money relative to usable living space than seemingly more luxurious alternatives.

I have seen the opposite as well. Building an efficiently laid out, beautiful building doesn't take that much more raw material, it just requires more thought. Big US cities used to also have copypaste mass housing even a century ago, built with a strong eye towards cost efficiency, but designers also kept aesthetics and livability in mind.

And since they were basically identical to each other, they had to figure this out only once, and they could build the same t

The 'cheap and nasty' design school usually succeeds at the latter, not so much the former.

And this supposed efficiency of modern architecture often doesn't really show up. The Empire State Building was famously built in a year. Nowadays the most utilitarian housing project takes longer.