I'm a bit behind due to not being here yesterday and there's been a bit posted in this thread, but I'll try to cover it as best I can.
Three over-arching thoughts with which to begin:
1) Using the system provided in Merchant Prince is a great starting point, but bear in mind it has its limitations. It offers a good general baseline, but doesn't cover specific circumstances. For example, it doesn't offer provisions for population, other worlds in system, existing level of trade and so on. From the book's persepctive, there isn't much difference between trading to a pop 5 water-world with a farming colony and an isolated pop 10 waterworld.
2) Please remember you have the distinct misfortune of playing in a game where the Ref has a deep and abiding interest in Shipping.
3) Be wary of meta-gaming. Because of the above two factors, I may decide to alter book DMs without prior notice.
Bearing those things in mind, the common sense approach is certainly valid.
The higher value, higher margin approach is also very valid. Low value spec cargos are preferrable to an empty hold, but that's about it sometimes.
Hayden Marks:
1) At what point would we (or even could we) saturate a small market like Savigny, to the point that it would affect sales price. There are a lot of small markets in this TU and knowing a bit more about any unique aspects of trade due to their size will be important overall.
A couple real world examples which bound my thinking:
Bermuda (pop 4 - 68,000) - Not built for resource exploitation or self-sufficiency. Imports 10,000-14,000tons per month, or 1ton per five inhabitants. Exports 1/100th of imports, or 1ton per 500 inhabitants per month. It's also a great example of the effects of level of trade. It costs significantly more to ship a container to Bermuda than to Antwerp (over three times the distance) because only two ships service Bermuda, compared to hundreds servicing U.S.-Europe. (All figures 2008)
Vorkuta Gulag (pop 5 - 225,000) - Built for resource exploitation using slave labor, not built for self-sufficiency but standard of living in gulag camps very low. Exported 200,000-250,000tons of coal per month, or roughly 1ton per inhabitant. Imports unknown but thought to be about 15,000tons per month, or 1ton per 15-17 inhabitants. (All figures 1950)
One thing to remember, especially in this TU where shipping is scarce, is that planets in the Halowon sector have more incentives to be self-sufficient than the examples listed above. Nevertheless, a planet like Savigny with a pop of just over one million would probably be starved for trade up to at least 10,000tons per month and be able to absorb 100,000tons, or so, of trade per month.
In Savigny's case, the vast majority of trade would be from Espiaux. A single 95ton cargo shuttle could carry about 1,000tons per month, and much cheaper rates than a starship. So, you might want to concentrate on items Savigny with its harsh climate and Espiaux covered in water can't provide each other.
In general, though, Gypsy Moth probably won't be able to saturate any planet over pop 3 with goods unless it brings a lot of one specfic, low demand good. How many washing machines could Troy's Rock absorb? Probably less than the 1200-2400 the ship could carry.
Hayden Marks:
2) How trade codes compare with planetary descriptions. Jack’s suggestions regarding Oil, Wine and Cinnamon seem logical to me (outside of the meta-game rules) since all of these require a sizable amount of land to produce, which should be at a premium for Espiaux. Admittedly, Savigny might be filling some of this need, but that’s secondary to the real issue – Are trade codes the end all be all to positive or negative DMs on the Actual Value Table (or what MGT calls the Modified Price Table), or do write ups, descriptions, and events within the game universe come into play in such a way that they create die modifiers to the AVT/MPT rolls?
Trade codes are a start. Write ups, descriptions, and events matter. Grapes, for example, may not grow in Savigny's dry, dusty, windy climate, but some form of wood tree probably does. Neither Espiaux nor Savigny may have silver-streaked marble, but they probably have some form of aggregate (for cement). Espiaux may make appliances, but Alsace may have a cost advantage in production due to its larger labor pool and cheaper factory space. Savigny and Espiaux could each certainly breed household pets, but maybe not chinchilas specifically. Perhaps chinchilas are in fashion at the moment (if not this might be one trade good where Gypsy Moth could exceed demand - how many Chinchilas per ton anyway?)
Hayden Marks:
3) There was something else but I lost my train of thought.. ARGH!
Don't worry, me too. :)
Hayden Marks:
From my point of view, we are probably best served by avoiding extremes when it comes to trade. 5 tons of oil and 55 tons of other speculative cargo would be better than 10 tons of oil and the rest freight, simply because in my experience extreme inputs to most systems generally result in extreme outputs, either good or bad. A lot can happen between the buying and the selling. Also, no one has perfect knowledge of a given market; we may show up and be very surprised if we put all of our eggs in one basket.
Yes, diversification helps mitigate risk.