From my experience with 3D printers, you will need to manage your expectations.
For the home gamer the quality is so so. You'll not match the OEM finish of injection moulding. You will also need a good printer, good designs, and so on. Not that it can't be done but if you are going out to market on this it won't be cheap. If you are going to buy your own then initial investment is high and the time spent to refine will not be short. It would be the same if you go for ally.
I'm surprised that secondhand is so expensive and hard to find or that there isn't any off the shelf alternatives.