I wasn't very specific about the situation. You are right in the sense that trade makes sense only among equals, the rest would just be forced to give up their

I wasn't very specific about the situation. You are right in the sense that trade makes sense only among equals, the rest would just be forced to give up their possesions. So we have to assume this isn't possible. We can assume I am standing on a cliff they can't easily reach. Or perhaps I have a few muscular non-thirsty buddies with me.