But in that case that's already what the comment you were replying to was saying: that higher density results in higher costs. So I guess I'm confused about what your point is. Were you just trying to say you agree?
The high costs are because an area is desirable, not because it's dense. Density is how you do something to mitigate the high costs of a place like NYC. Imagine if you chopped off the upper half of all buildings there, what prices would do!
You could build a bunch of dense housing in Burns, Oregon and you wouldn't be able to charge much for rent there!