Injection moulding. Biggest cost is cost of the metal for the molds.

Not possible to have overhangs, as both halfs of molds need to be able to seperate.

Wastage of plastic due to runners need to feed in plastic.

Need a program that can edit step files.

Recommend FreeCAD. Can create step files. Possibly only one that can create step files.

FreeCAD can read KiCAD files.