What are you crafting?
Not in game at the moment but I used to do refined rock and I am pretty sure it has no spark cost associated to it.
I used to sell my refined at 13c and 22c for decorative and there was profit in there. Bear in mind that folk buy these rocks in bulk so even if it worked out at a small profit, you would make that small profut thousands of times per customer.
It was quite common that someone would spend 10k coins each purchase for refined.
I had same price on the wood as well.
Not questioning your pricing, just offering my working out when I did it in case it’s of any use
Edit : decorative has a 200 spark cost plus the wax - I costed spark at 0.01 c as when you work out the spark output on soft coal / cost it’s almost nothing to be honest.