A method for transacting exchanges of agricultural products involves observing the price of an agricultural product at observation points over a period of time. In one embodiment, a maximum price is specified. For each of the observation points, the maximum price is selected when the observed price is greater than the maximum price, and the observed price is selected when the observed price is less than the maximum price. A price is calculated for a quantity of the agricultural product based on the average of the selected prices and a premium. Individual contracts can be aggregated to reach more acceptable trading quantities and intervals, enabling participation of a derivative hedging products service provider and intermediate parties such as elevators and elevator services companies. Aggregation can be carried out manually or automatically, and configured to support anonymity of various parties in the transaction chain.