Q. I don’t get why downtown high-rise housing isn’t cheaper than suburban housing.

A. There’s one big economy of scale when building downtown, because a high rise puts many more housing units on a given piece of land. But that’s more than outweighed by higher land costs, the complications of working around existing buildings and utility systems, and the need to use expensive steel frame construction. The space devoted to elevators and hallways, underground parking and storm water detention, and water pressure and fire suppression systems also drive costs up.