Scenario: The planet China manufactures iPhones that retail for Cr200 (1977 price). In a 1.5m x 3m x 3m space you can fit about 28,000 packaged phones. For each parsec shipped it costs 3.5 "cents" per phone.
So for relatively small, high priced products you could ship them all over a sector from one planet economically based on macro econ comparative advantage situation like China and iPhone manufacturing.
Something to think about in the T.U.
Thoughts?
What is the point you are trying to make? That you can fit more small things than large ones in a given space?
Traveller MGT2 does not give quantities of goods per unit volume (you can try and reverse engineer it but it rarely makes any sense) - is that the point? There are no goods that cost MCr5 pr Dton. Common electronics are Cr20000 per Dton and phones are as common as they come. If you are using Cephues trade tables then the number will be differnt but they still won't compare to your example.
Reducing the margins and making prices more attractive by shipping goods from one place to another by cheaper and cheaper mechanisms is arbitrage not comparative advantage. If you can make a phone locally for Cr200.032 then don't need to buy the planet China ones. Presumably the presumption here is that planet China can make phones cheaper than any other planet, but how far does that advantage spread, if they are the cheapest for 10 parsecs it still means that a planet 8 parsecs away can still make them for Cr200.28 and still be better value than a planet China import.
In traveller there are only a few limited conditions that make goods cost a particular amount. The broader you spread your net the more likely you will encounter a planet that has the same advantage. Any systems closer to it than planet China will be better off buying from this other planet as they won't be shipping it as far and their shipping costs will be the same per item/parsec as planet China.
Comparative advantage is concentrating on manufacturing the goods you can make most efficiently, If planet China isn't buying the Cars you make in exchange for their phones it doesn't really apply. You don't mention the other planets and what they might be making that planet China buys (raw materials maybe). If you end up making phones for Cr1 per Dton more, but it means they buy your cars for Cr2 per Dton more than you can sell them locally then the trade benefits both parties and you can leverage comparative advantage. If they are not allowing you to pivot manufacturing to expand you market in things you make efficiency then the requirements to leverage comparative advantage are not met.
The freight cost is not the only consideration. You don't sell individual phones from the container they go through retail. The costs of all that will swamp the Cr0.032 saving on shipping.
Cr200 manufacturing cost is also somewhat meaningless. In MGT2 a mobile phone is arguably an Improved Mobile Comm (CSC p63). That retails at Cr150 when manufactured on a TL8 world. The retail price of one of those at the average world that has a TL12 starport would be less than Cr10. This aligns far more favourably at the packing density you mention with the KCr20-25 per Dton of common electronics. 0.032 is a far greater element of a Cr10 item than a Cr200 item.
Raw materials costs should be in the order of Cr5 per phone (based on the raw materials costs wrt. fabricators), it could be as low as 20% if we allow the 2d6*10% rule) Canny purchasing could reduce the cost of those raw materials further as trade goods swing between 15% and 400% of the base cost. Using those rules we have the cost of raw materials swinging between Cr0.3 to Cr48 per phone. once you have paid for the pattern and other capital costs the manufacturing cost per phone is power and rent. Power costs are negligible at this level. My finger in the air calculation means you can print 2 phones in 2 hours per litre of TL12 fabricator for KCr10 for the fabricator. You need to make 2000 phones to pay for the fabricator and the raw materials to make them over 100 days. You can halve the fabricator cost by using the fab in a quadruple chamber. It will make 8 phones in 8 hours, but you only need to make 1000 so the overall time drops to 50 days.
If planet China is really good at manufacturing, Traveller planetary design rules mean it is not a good source of raw materials and thus it has to be an importer. Any shipped goods will likely pass on the shipping cost to the buyer. That is where you will get your comparative advantage. Planet China is likely industrial but it could also be poor. An Agri or Garden planet which is its best market cannot be poor. For planet China to be the most economical producer it needs to have a low sale cost for its goods but on average it is paying more for its raw materials than its potential customers do. If all they need is a fabricator (and for small goods not much of a fabricator either, it is going to be at a disadvantage.
Of course Comparative Advantage assumes you value work on all outputs at the same level. If you think art is a more important use of your people's valuable time then you might be willing to pay over the odds for mere technology if it frees up your populations time to write poetry. If planet China thinks poetry is a pointless foible they may not value the same amount of work put into poetry as that put into making phones. If the poets need to dedicate 100 hours on poetry get 1 hours worth of phones they would have to be producing phones at less than 1% of the efficiency of planet China before it made sense to trade with them. If they see them as barbarians for not valuing culture they might decide not to trade with them at any price on principle.
Comparative advantage is a fascinating theory of economics, but it is more a tool to generate thought and discussion than a proven paradigm.
