> the interplanetary equivalent of sending coals to Newcastle
Famously, one man did this, Timothy Dexter. He was the world's worst businessman, but luck was with him every time.
Buy a buttload of worthless currency issued by a country destined to lose a war to the British? He was the one laughing when the British lost and the newly formed US government paid out. Ship bed-warmers to the West Indies? Well, turns out they make great ladles for molasses manufacture.
Same with the woolen mittens he sent there; His ship got there at the same time traders were leaving for what's now Siberia.
On to the coal. Someone suggested, as a joke or as an insult, that Dexter could make money shipping coal to Newcastle.
So he did.
His ship hit the harbor at Newcastle the same week the coal-miners went on strike and he was the only game in town.