In the selling price calculation apparatus the request receiving unit receives from the purchaser information concerning the ballot tickets the purchaser wants to purchase. The sales information acquisition unit acquires from the discount DB information concerning the ballot tickets. The sales information includes the accumulated number of purchasers and the predicted number of purchasers. The discount rate calculation unit calculates the accuracy of statistical odds based upon the accumulated number of purchasers and the predicted number of purchasers, and calculates the discount rate based upon the accuracy of statistical odds. The selling price calculation unit calculates the selling price of the ballot tickets based upon the discount rate. The problem that the sale of pre-sale ballot tickets becomes concentrated immediately before the time of stopping the sales of the ballot tickets is relieved or solved by a series of processes thereof.