I have yet to be convinced that much star trade at all will make any economic sense (sure, information, and luxury goods, but commodities?).
Depends a little on the rules of the game, but in Classic Traveller, it costs 1000 credits per Dton per parsec.
Shipping a water-like liquid (or anything with a similar density), that comes out to 14,000 kg shipped 1 parsec for 1000 credits.
Translating that to modern currency, that comes out to 14,000 kg shipped 1 parsec for about 4000 (euros).
That makes shipping costs about 0.4 euros per kg or 0.2 dollars per pound per parsec.
Let's ship coffee beans at 11,500 lbs per dTon ... or 0.35 dollars per pound per parsec.
[Retail price of coffee is about 4 dollars per pound, so a 9% premium (per parsec) for Interstellar Imported coffee.]
[At real world launch costs, it makes no sense (even to LEO). At Traveller ship costs, interstellar shipping costs are trivial.]