@moth_ball
My brief answer is there is no limit.
My extended answer is I would pass legislation to make such manipulative monopolies illegal and force the corporation who developed the cure to provide at comparative price margin compared to the limited cures of other ailments which should already be organized at reasonably afford level to the consumer.
Punishment for not complying with such ordinance would be the forceful (after lengthy and repeated attempts to work with said corporation) seizure and public distribution of such material in the name of humanitarian aid.