Let me know when your 3D printer can make it's own electronics. Also, mining equipment... I mean, wow. I suppose sintered metals might be possible but there's still the refining of raw materials. I guess my point is that the supply chain needed to build a 3D printer is probably enough to sustain things without the 3D printer.

That's not to say they wouldn't be useful. I really like being able to sketch out whatever bracket, holder, candy dish, etc that I want and print it. That would be very useful on a world without a huge economy providing every little thing you might want or need.