I have a home 3d printer myself and it is great for proto-typing parts for fit and function but it has some drawbacks as often larger parts may lift and or not stay perfectly flat, show alot of lines and are hollow. Also another drawback is that they don't like heat and direct sun.
Shapeways and imaterialise provide a great service and their products are laser bound and therefore are solid filled and not hollow so more stable especially in heat and sun. They offer alot of variety but with somethings like nylon, the finish is not glossy - hopefully that will come one day. In edition the prices are not the cheapest but when looking at the perspective that they are making a one off piece specially for you it isn't bad and in some instances the parts there are keeping some games alive. As for me I do it more for the fun and challenge and I like to help pinheads with no longer available parts along the way. As for me my cut from any sales is only 15-20% for my efforts and the remainder is shapeways.
as a example my Snackbar mods are made from parts printed by imaterialise as they offer a better deal on batches of larger parts but are much more expensive on smaller one off parts. I undercoat these and then give 3-4 coats of colour and they are solid and look great.
then you can print custom polished brass plunger knobs - not cheap but no other way to get this done for the same price, not even a machine shop can match this
sat dish (slightly modded for Goldeneye) - was getting real hard to find and then this has panel lines for a more subtle modded look
to then making custom tools - bulb tester and for comparing bulbs - wedge 555 and #44/47's and Comet Matrix gear
to fin mod combined 3d printed nylon, acrylic and polished silver just needing leds to add interaction to a game.
sorry for the self promotion but just examples of what can be done and looks great straight from the postage box from the print houses (except the snackbar mod - is painted)
ps - latest pinball parts in order of newest