This technique uses Structural Insulated Panels (SIPs):
This video describes a very interesting project – it is a house built for less than $3,500. Obviously such a house will be relatively small (128 square feet). Not so obviously it is built on a trailer frame so it can legally be that small. And a great deal of the material used to build the house is recycled from prior structures, keeping the cost at $3,500:
More info on this type of house is seen in this second-gen version:
Definitely not $3,500 however.
While the original house does have innovative features, like a roof that opens, the lack of things like modern restroom facilities may be a deal breaker. Here is a house-on-wheels that is just a little larger and solves that problem:
Buying an older RV trailer might be a way around this problem, as it has a sewage tank. See Using an RV as a home for ideas.
He notes the difference between this house and a tiny house is that this house is 12 feet wide. Tiny house are usually more like 8 feet wide. Here is an example in that size range: