I am an engineer / program manager at a company that builds radars, communications systems, and other items for the military and commercial applications. We use this technology to build prototypes of some of our subsystems, for fit checks, thermal / airflow analysis, or simply as a sales tool (amazing how having a model in your customers hand works for selling something!!). It is relatively affordable, particularly compared to previous methods of prototyping, and very very quick. There are a number of companies here in Southern California that make a good living doing this type of work. We send them a 3-D CAD model, and a week or so later, they deliver a part.
Keith