>However, after years and years of very slow building, the amount of pent up demand is such that even if builders were allowed to construct houses, the houses would almost all be built for the very well off. The amount of houses you'd have to build before you started constructing truly affordable housing is immense.

I hate the term "affordable housing". All dense housing construction helps make housing more affordable - after all, you'll be convincing people who can afford it to move out of "bad" housing into the nice stuff you're building.