I own a tiny manufacturing company, and I have used 3D printing extensively for prototyping and mold masters. It's fantastic to be able to get a mockup of your design for $10-100 in a couple hours rather than paying a machinist $65/hr to work on it all week. Perfect for checking the ergonomics and improving your ability to visualize the relationships between parts.
But then when you go to manufacture, you need to get parts for under $1, not 10 or 100, and you need them popping off the line every minute, not in a couple of hours. Plus the vast majority of 3D printed plastic parts are fragile because they don't have fibers (such as wood grain or glass or graphite) running through the part. Dimensional tolerances are also an issue--some printing technologies are very precise, but they cost. The cheap ones are as precise as their cheapness suggests. Injection molds let you churn out 100,000 parts a month for pennies apiece with much tighter tolerances in a much greater variety of materials, including some that are very strong.
Metal 3D printing has come a long way, but a small part that might cost you $10 to mass-produce with CNC machining or investment casting will cost $700 to print, with no volume discount. Literally, I priced that out a while back. The parts thus produced are not as strong as proper forged parts, but they are surprisingly strong. I don't know if they'd take the force of a bass string or not.
So a 3D printed bass would be a neat novelty, and might let you explore some things, like weirdly braced sealed chambering, that would be tricky with conventional construction. But absolutely nobody is going to mass-produce anything that way.
