so, something like "a horse for a horse" but never "a horse for a goat" type of thing? What if a person with like 5 goat wants 1 horse.... they cant trade a goat for a horse. what if they go by weight. anything weighing equal to this here horse is what you give me... so guy's 5 goats weight equal to the horse. he trades his 5 goats for 1 horse. i kind of like this idea, and it is also a way for them to boast how moral they are. a human might stuff their horse full of food the day of the sell just to get more out of the poor goat guy or stuff his horse so that the goat guy cant afford it. Where as the aliens are (BELIEVE they are) more honest than that. But then, the tricky side of this would be, how would you do this with food or services?