I asked myself the same question some time ago. This is one of the answers I got that might be helpfull to you as well...
Sculpting:
A 10mm single figure costs about $80 to get sculpted.
If you plan on making the sculpt/sculpts available for other buyers you need to take into account the mass production. Spincasting if you want them in metal.
Spincasting:
You need a Master mold. Costs about $50.
Cleaning and prepping the masters cost about $80
A production mold needs to be made and costs about $80
A production mold fits about 24 miniatures and gets around 300 spins before worn out.
Then there is the matter of marketing, packaging and shipping. No idea.
Resincasting:
No idea. But I'd say you need good equipment to succeed with resincasting in 10mm. This statement is based on my own small little experiments
I do not have any leads on sculpters but I hope this information helps. Cheers!