The article proposes a mathematical model to support decision-making on the volume of purchases and the level of retail prices, which the wholesale company (dealer) sets depending on the manufacturer's selling prices and the demand of end buyers for various volumes of wholesale purchases. It is assumed that the manufacturer and the wholesaler influence price through pricing policy. As a result, the problem of determining the optimal volume of wholesale purchases and sales, depending on supply and demand, as well as changes in the level of purchase and selling prices, is posed and solved. Two options for setting the problem are considered here: when the end buyer is informed and not informed about the producer's prices.