Final answer:
The disadvantage of an exchange cart or barter system is the difficulty in using perishable goods for future transactions, such as a farmer buying a tractor with a future crop, due to uncertainty in value.
Step-by-step explanation:
A disadvantage of an exchange cart system, which operates similarly to the barter system, is the difficulty in entering into future contracts for the purchase of goods and services, particularly when dealing with perishable items. For instance, if a farmer plans to buy a tractor using a crop that isn't harvested yet, such as strawberries, there is a lack of certainty regarding the future quality or quantity of the crop, making it a risky and unreliable form of payment. Moreover, the barter system can hinder the growth of smaller economies because it is not scalable and adaptable to larger or more complex transactions.