> As long as construction costs remain below the value of the units all-in, there's profit motive for developers to build.
Not true
Real estate development is extremely capital intensive and therefore it's a question of all-in cost of capital compared to other investment opportunities.
The opportunity cost has already factored that in. Unless you think cost calculations are arbitrarily forgetting to include certain costs for no reason?
Well for sure in the actual financial models yes, but it's demonstrably true that most HN commenters here do not know this is how to think about the question of returns.
And FWIW "opportunity cost" doesn't really show up as "a cost" in the traditional sense.