Okay! So, I've finished off some more of the item/person interactions, and realized that probably, I should work on the commodities/trading system.
I.e., how do you collect and trade cargo and such.
Four types of commodities (for now): material, mineral, food, and fuel
Each type has a "high" and "low" classification, that is, high minerals are complicated things that higher tech civilizations would trade in (e.g., radioactive uranium crystals) whereas low are what lower civilizations would have (e.g., dry dirt)
Now for the price system, I really am not sure what to do. It seems kind of lame but I think I may just use biorhythms for now, thus, prices fluctuate according to that sort of thing. It's convenient because I only have to compute things when they are needed, i.e., I can easily use it as a function price(T) rather than have to implement some whole dynamic system which will probably not even be noticed that much by the player. I can add "dynamic" elements to it, like maybe price spikes or dips depending on what you do, but the base price fluctuation will rise and fall on biorhythms.