It's not quite as simple as you make out to make tooling for injection moulding plastic, and for low volume sales, which the chaldron will be, will almost certainly be uneconomic.
Just consider the quote for a wagon wheel centre to fit an available rim, which I needed, was over £300 and go from there, patternmaking is not cheap in any medium.
Just think how long it takes to research and scratchbuild one side, one end and the chassis of a basic wagon, which is what is needed for a simple wagon kit, and then multiply that by around £15 per hour and you will have a rough idea of the cost.
Remember you are paying for the skill of the patternmaker and the cost of the machines he is using, for simple plasticard masters this will only be a rule, square, knife and glue plus the research and ability to read(and probably make) and work to a drawing, still not cheap, but not as expensive as the thousands invested in machine tools for making injection moulding tools.
My offer to look at resin casting the kits still stands, but I will need some one to provide the patterns as I no longer have the time to do this. I think it would be best if the patternmaker and I met so that what he made was compatible with my production methods.
Phil Traxson
Port Wynnstay Models