A few thoughts, After reading a little http://books.google.com/books?id=Y1DEs7XWir0C&printsec=frontcover&dq=money+in+the+late+roman&hl=en&sa=X&ei=4CVfUtqLJ8LW2AXojYHIBQ&ved=0CC8Q6AEwAA#v=onepage&q&f=false Should we consider storage life and time-to-consumption in the logistical chain for grains and meats or is that too mico-manage-e? It would require us to consider rate of consumption of individual actors, weather factors on degradation of the foods (and supply of said food) and also technologies would come into the question(better storage tech, production tech). For example a player could research earthen vessels to store grains. Or research an improved grain (they could for example choose a grain with better storage properties but lower nutrient value). Or perhaps better storage buildings. Further the timing of a player selling a grain is important, if a neutral or friend doesn't have such good storage (either for poor grain technologies, or poor storage technologies) and are now in the winter with dwindling supply (and assuming crops are affected by season) of grain we could trade out grain for metal(or whatever). The markets could be left to run themselves, and technology levels could dictate how efficient the trading ai is. Also, what about other important resources (common salt, leather, saltpeter [very important to the storage of meats!], lye etc). Not to even mention wines... oh the tech trees we could design for the histories of wine and its trade.... just some thoughts