I was watching a project that involved making a bunch of plastic parts. The total volume was in the low thousands. It was enough parts to start thinking about t

I was watching a project that involved making a bunch of plastic parts. The total volume was in the low thousands. It was enough parts to start thinking about the scale but not enough to make molds worth it. It seemed like the breakeven point for molds was around 20-50k parts depending on the mold. The design that was used for the final product was made super fast custom made reprap printers with rather low accuracy. Due to the unique abilities of 3d printers it ended up being very strong and durable with a honeycomb structure inside. 3d printers are at the point were for some applications it makes sense to use them in production. The exceptions are high volume as well as very low volume that has high strength requirements( and even then for metal printers some stuff can be done post-manufacturing).