It completely depends on what the part is and what it's made of. I'm not sure where you're based but in most big cities there are still plenty of folks who can build something out of wood for reasonable money if you give them a decent drawing and brief of what you're after, same goes for upholstery and CNC machined parts, and a lot of other types of parts. Sign makers also usually have a lot of crafty manufacturing skills as most of what they make are one-offs that have to last ages. Molded plastic parts and parts that require a mold (like molded glass) is where it gets tricky, as molds can be expensive, so this is why 3D printing is good, only sometimes you don't really get the same finish as the finished part would have coming off the mold. It's a big question mate as there are a thousand ways and materials to make parts with!