Continuing the thread from last time, I'm looking at some interesting stuff. First would be a modifier for the world based on population, status, and Tech Level. This modifier will not change very often, so it can be written down. Next is current market conditions - normal, bull, bear, recession, inflation, depression, etc. This number is is rolled randomly every 6 months or so of game time, and modified by the general economic conditions. The form this number would take would be a difference from the last time in steps, which are read on a meter. Gaining 2 steps from last time might pull the world out of the recession it has been in, or it might push a vibrant economy into overheating. The general economic picture of the world is thus clear. If you have a small economy, it is more labile, more liable to change, than a larger economy, but it also heals faster. This is background, GM-area information.
Specifics are the PC area - whether you can sell your cargo at a profit or not. Goods not only cost money to buy, they cost money to haul, and they cost money to store. Rich cargoes mean you pay more for them, but they take up less tonnage, so we can treat quality as a tonnage modifier. Basically you have to haul X times as much of a bulk cargo to make the same profit as a rich cargo. Storage and haulage cost by the ton. You might bring a cargo in and find it would be better to sell for a small loss than to have to cart them to another system. You would roll for each cargo under the column of the current economic condition.
You can also do other things - haul for a smaller guaranteed profit; take passengers; create, buy, and sell Intellectual Property; etc. Some might be safer but have less potential, others might be riskier for more potential reward. IP and such intangibles have the great benefit of costing nothing in mass, and thus having no haulage or storage costs. These have yet to take shape in my mind.