If you want to make a million copies of something, Jacdac is unlikely to help you much outside early prototyping. OTOH, if you want 10 copies of something it may simplify things - you don't have to solder any wires 10 times. If you want more, you can get a PCB with holes matching holes on modules and screw them in with M3 screws (skipping the cables - the holes carry signals), or solder them down.

Gold plating is not strictly necessary, depending if you plan to use the plug thousands of times.

Edit: also very good observation on top of the comment - Jacdac is indeed a way to bring "modern" software engineering practices to hardware design.