It's like anything else...if you want a good product it isn't cheap
Your typical 3D printers won't give you a smooth product and normally those using them lean toward ABS plastic....not great with the tabs on these end pieces...they will break
Nylon and higher end printers run up the price....and they are not fast either
The tabs on the mag extensions that I received from Chaz (Cotis) were not molded into the part, but were seperate pieces that were glued into slots in the mag extension. Don't know if that makes 3D printing any more viable, just throwing it out for discussion....