They can still contribute in keeping the cycle going. They don't need to set the prices to rip someone off, writing a shitty prescription does the job too.
As a costumer, I can think of several who are more interested in money than curing patients and do a lousy job. Even kill patients out of their carelessness or create another problem while solving one in the worst case scenarios.
Such people exist in every field. Teachers, politicians, engineers, cops, entrepreneurs, even organizations that are meant to help people use the donations money for their own selfish need. Unless you believe doctors are some superior beings who have ascended further from human nature like greed, selfishness, laziness, incompetency and the likes, I don't see how saying "Nooo, all doctors are awesome. They only care about their patients. They always do the right thing." makes any sense.
That being said I reckon good people are the majority out there, in general.