I remember one thing in "Se questo è un uomo" (If This Is a Man) by Primo Levi. In Auschwitz camp, where money, trade and basically private property rights were abolished and where they tried to destroy all what makes people human, Primo Levi mentioned there was always trading. More than that even some informal "stock exchange". Every object (food, cigarettes, shoes, etc) had a price and it was fluctuating based on the laws of supply and demand. This makes me think how exchange is deeply engraved in human nature.