Can $2,000 build a whole house? Even in Haiti? I would think 10x that for anything we would call a "house". Its not surprising there is a vast unmet need in Haiti given its poverty and the scale of the disaster.
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.
Haitians aren't looking for 2-car garages and island kitchens. Running water, electricity, and a structure that won't collapse in the next natural disaster would do just fine.
I imagine a challenge with deploying manufactured housing to Haiti is that anything new that's built needs to be earthquake-resistant.