Manufacturers sometimes discount the price of a product to retailers for a promotion period when the product is advertised to consumers. Such promotions often result in a dramatic increase in amount of product sold by the manufacturers to retailers. Nevertheless. the manufacturers could often make more profit by not holding the promotions.
During such a promotion retailers tend to accumulate in their warehouses inventory bought at discount; they then sell much of it later at their regular price most strongly supports the claim above about the manufacturers' profit.