Habitat, which has built several hundred houses in Haiti, estimates $4000-$6000 per "core house"; core houses are expandable, seismically sound permanent housing structures.
Habitat also estimates 105,000 "totally destroyed" pre-quake houses.
Obviously, all of these numbers are better than the six houses the Red Cross built.
The larger problem in Haiti is legal, though: getting the rights to land to build on is complicated and slow.