There are two general ways to reduce cost. The first way is to utilize an advanced or innovative construction system that reduces labor, reduces construction time, or utilizes unique materials. This will either reduce your labor cost, construction period and financing cost, or material cost. Different approaches to PreFab attempt to tap into this, but so far the success is in making Modern Design available where it was not before, but the cost is still higher than status quo on-site construction. Economy of scale is required to make this kind of approach work. The second way is to leverage construction means, methods, and materials already in practice in the home building industry, using modern designs conceived with this in mind. In this way you are not asking crafts people and construction workers to do anything out of their normal day to day operation, you are not using materials that they are not familiar with, existing material supply chains can be maintained, the construction industry's business model is not expected to be revolutionized. You ride the economy of scale that the entire home building industry provides. Everything you build modern will fall to some degree into one of these two approaches. The closer you can get to either extreme, then the more affordably you will be able to build.