PCB printer - etcher
When i was at school (technical school) we had a chemical etching lab, which worked with photoresist-prepped PCBs and UV development, and ferric chloride etching. It was very bulky and involved the use of hazardous liquids.

There is also a way to do that at home, using laser printers and ironing the design directly on the copper layer, and then removing it with some acid. But AFAIK this method is not very accurate.

I've seen also a CNC (as other described) machine (of the size of a microwave oven) that use cutters to directly remove the copper layer and that works on gerber files (generated by the CAD software). It takes about an hour, depending by the complexity of the design, and i think it could cost some hundreds (thousands) bucks.

All these machines can only create single layer (at most dual face) circuits. For more complicated things (multi-layer PCB) you need to refer to a specialized company.

As ceconel mentioned, the price for manufacturers scales very badly for small numbers; could be that 1 piece costs you only a bit less than 50, and it's due to the fact that they use masks, which are the most expensive part of the process.