Since everybody has a different 3D Printer and therefore needs a different 3D Printed Adapter Housing, there is no point to 3D print the parts in-house and charge you extra money for that. This would just unnecessarily increase the overall Extruder price.
For this reason, I made it very easy for you to just 3D print the plastic Extruder parts yourself, which gives you the freedom to use my Extruder on a big variety of 3D Printers without the need to buy extra adapter parts.