I don’t see 3D printing as being competitive with normal means of mass production. It will dominate prototyping and small scale part production though.
I think that you are right; it is hard to imagine 3D printing being able to compete with normal mass production methods in the near future. It will continue to become more affordable and useful for home enthusiasts with some niche opportunities.
We are planning on moving soon; when we are settled in I am hoping to purchase a computer controlled milling machine or put together one from a kit. I believe there are currently more opportunities to make money using a CNC router or milling machine.
Ten million 3D printers is mass production.
Before you say "ridiculous," would you care to hazard a guess as to how many servers Google owns?