Your car analogy conflates scarce and non-scarce goods. A better car analogy would be that someone invents a way to create cars for $200 with 3D printers, and so everyone stops buying cars that cost 100x that much. "You wouldn't download a car" and all that. Of course, someone has to create the CAD designs or whatever, but that's a much smaller industry than all the manufacturing that existed before (so, of course, all the people who work in auto factories are upset that they've been made irrelevant).