buy a couple thousand of them lol.
1 of anything is going to be expensive. even 20 is still going to be much more expensive than mass produced.
There is a massive amount of work involved just to get to the point of loading material into the machine. measurements, modeling, detailing, thinkning through the process so that it can be done in a somewhat efficient fashion. There are also some things that just do NOT carry over well from injection molding to machining. IE square internal corners. They may be neccesary to fit internal parts but are not something you can mill. At that point you need to rethink the design or go to another process like EDM. While I have an EDM, it is a slow as dirt process. What I can remove in 5-10 minutes on a mill might take a day on the EDM. Just squaring up internal corners to any appreciable depth is like an hour of machine time on the EDM, plus the time to design, setup and machine the "tool" no the mill.