3D printing is not like that. There is already an entire set of industries built to produce widgets. 3D printing doesn't offer any benefit except for customized items. So how often do you need something customized? No matter how cheap 3D printers are, it's always going to be cheaper to get somebody else to print a one-off for you using their machine. You don't use it all day multiple times a day. You pay them for that one-off, and then you don't need a 3D printer again for a long time.