[Randover]

Aside from list of trade good prizes. Story beats Math.

It's great to have detail, don't get me wrong. But the big building stones of your adventures are better without complex economy.

If anything I would focus on one type of trade good. Weapons, Cloths etc. This way your players stand chance to understand all the relations. Being the general traveling merchant is realy hard (both on GM, and players). Sure they could use great opportunities in other commodities, but we all need some guide-lines, something we understand.

The math part you want to avoid is calculation how much profit players need from this job, to be able to do the next one. Or at least to keep the progress of story going. Volumes of goods, days of travel (travel rations), fair market values and taxes (fees for using roads and bridgess or entering towns). All this can overhelm GM and players quickly.

I would build it more abstract and GOAL orriented.
1. mission - Turn profit in trading spices
challanges - a/ local gang will try to bully players
- b/ make deal with local merchants (not only buyer, but also the competition - unless Win/Win solution is found futher bussiness can be crippled)
- c/ some other side-quest that can yield good intel for next trade opportunity and progresses the story
- d/ plan your next move based on intel you have (here players could deside to do riskier stuff, agree on goals as profit could be means to other end. (wedding, revolution, exploration...)