Because there is a good chance that X is going to be less than what either you or the cardiologist already make, but it may be more than what a janitor does mak

Because there is a good chance that X is going to be less than what either you or the cardiologist already make, but it may be more than what a janitor does make. So the cardiologist and you keep working, and the janitor has an incentive to quit performing a mindless job... and maybe become a cardiologist.