Consumer and Producer Surplus In panel (a), the consumer surplus from purchasing quantity D1 at price P1 is the area below the demand curve and above that price. The consumer who purchases D2 is willing to pay price P2 but has to pay only P1. The difference is the consumer surplus and represents the satisfaction of consumers over and above the amount paid. In panel (b), the producer surplus from supplying the quantity S1 at the price P1 is the area above the supply curve and below that price. The supplier who supplies unit S0 has marginal costs of P0 but sells it for P1. The difference is the producer surplus and represents the return to fixed factors of production in the industry.