The material for Ronja is quite cheap. What is most expensive on Ronja is the work. However, fortunately, most of the work is related to organization of the manufacture - finding tools, managing the pieces, transport, shopping...
It is possible to save time by manufacturing many pieces of Ronja at a time, and then the organizational work is saved. Furthermore it's possible to outsource some operations to professionals, which can do it quickly and still reasonably cheap.
These operations usually pay out if you have them done by paid professional when you are making small quantities of Ronja:
These operations usually pay out if you have them done by paid professional when you are making large quantities of Ronja: