It’s important to note that the declining prices that accompany genericization are based on the market, and the market doesn’t always cooperate. Sometimes generic competition never materializes — which may be the case for drugs that are particularly difficult to manufacture, or drugs that serve a very small number of patients. Without competition to put downward pressure on price, a brand manufacturer can continue to sell the drug at the market rate.
Different types of market forces can cause issues with generic pricing. In the case of some generic drugs that are dispensed at hospitals, large purchaser groups can drive down prices by contracting with the generics manufacturers who will sell a drug at the lowest price. When enough manufacturers are driven out of the market and a remaining player runs into a manufacturing problem, this can cause a drug shortage. Prices might temporarily rise to attract new producers or so that an existing company can expand manufacturing.