[bombcar]

One of the problems is that the people who need housing aren't buying new houses.

Nobody is going to spend $x on a brand new house without having some say in it, and so those houses tend more and more toward "high end/luxury". After all, why go through the hassle of all the paperwork and building and NOT sell for the highest price you can get?

Same thing happens with cars; the market for car buyers is much larger than the market for new car buyers, but only new cars ever get made. Nobody is making used cars, or even the absolutely cheapest possible, which affects the whole supply.

[bluGill]

Most new houses are only slightly custom. You generally start with a floor plan from the builder, and then choose the color of the walls or other minor details. Sometimes a new house is cheaper than a used one because you can move into a used house much quicker, while a with new house you have to wait for them to finish. Usually a new house is more expensive than a comparable used house, but not by much. Even a fully custom home is generally not much more expensive because your builder will tell you what costs a lot of money (if you ask for 8.5 foot ceilings the builder will talk you into 9 foot because those are much cheaper since precut parts are available), and what is insignificant. Generally walls can go anywhere and are cheap to move around.