i am not really good with economics also, but what i understand is the price of something is what ppl would pay for it.
So instead of figuring out how much it costs you to send the companions to gather the materials, instead try to figure out how much the materials sell for.
example: it doesnt matter if you can get 1 desh for 18 credits, what matters is ppl will pay 49 credits to buy one.
so when you create an item that is made by 10 desh, you shouldnt charge less than 490 credits, if you do you should instead sell the desh directly.
Good point but don't forget that there are many instances where what people will pay is less than your cost. This is due to people not paying attention to what it costs them for the material, let alone their time and then putting stuff on the GTN at a loss. To each their own.