Cheap printers will not be printed. the same technology that makes 3D printers possible makes cheap injection molds possible too, and injection molded parts are so much cheaper there is no comparison.
VOLUME is everything! Cheap happens when you make tens of thousands. Really cheap happens when you make millions. A little example. I know a company that bought some switches for their prototype of a product from Radio Shack for $.79 each. When they put it into production and bought a case of 10,000 loose switches they got them for 1/2 cent each!