This is just a form of supply and demand. More people want to do $desirable_job or $satisfying_job (and there's plenty of overlap), so you don't have to pay the

This is just a form of supply and demand. More people want to do $desirable_job or $satisfying_job (and there's plenty of overlap), so you don't have to pay them as much, because there's always another person in line to take the position.