There's a spectrum of how you get PCBs assembled.
1) Have a human pick out all the parts, solder them all on by hand, and check them all by eye. Low cost of entry. Good for low-volume high-mix work. Surface mount is difficult/impossible, depending on the package.
N) A pick-and-place machine, wave soldering, and automated optical verification. Very expensive equipment. Only cost-effective at high volumes, 100+ at least. Through-hole is difficult/impossible for some pick-and-place machines.
What's in between? Reflow ovens? Automated solder paste dispensers? Some sort of automated part dispensing system that's between a wall full of bins and a pick-and-place machine? Stuff I haven't imagined?
The bigger question is this: what steps can be taken to increase the efficiency of an entirely hand-solder operation? In what stages can such an operation make the transition from all hand-soldered to fully automated production? And what is the cost range on the equipment involved?