I think the key is the word "printer". Look what happened with printing. "Printer" used to be the name of a job (as was "computer") and being a printer was a respectable and valuable trade. Computer printers used to be terrible chain or belt devices. Later they were replaced by the cheaper and about as bad dot matrix systems. But over time they improved, until now the print shops that all big companies and government departments had down in the basement are gone. The printing businesses downtown are mostly gone -- the few that stay in business do specialized tasks.
Cheap, ubiquitous assembly will become common, just as cheap word processing became common. And like word processing I expect more custom and on-demand parts -- perhaps to start just phone cases and replacement parts for that umbrella (the 3D equivalent of early Word Perfect documents with lots of italics). But soon enough we'll print out plenty of stuff that we today would buy, if it is even available, just as we generate all sorts of documents.
And just as with printing, where we print less and less, perhaps we'll use less and less when we can fix or reuse things instead of throwing them all away.
(and to think I used to consider "3D printer" a terminological overreach...at least I can learn from the past)