3D Cars Manufacturing Conundrum
Reducing labor costs actually means fewer people working. Success of this kind produces the quandary once voiced by Walter Reuther, the famous union organizer. When the technology succeeds (and it will) who will be able to buy one? (as the US poverty rate continues past 25%)
In a funnier, but still true observation, Steven Colbert said the cost of the printer is the ink, not the device. Unless the parts are made by solar absorbing bacteria, the plastic will just be more expensive petroleum, negating the mileage gain and continuing the addiction to Mid-East politics/wars/defense.
Every miracle brings new problems.