Generally, it implies he is more valuable because he does a job which is in high demand but whom few people can peform. Hence there is high demand but limited supply so companies pay a lot of money to garner this rare and precious commodity.
The higher the skill requirement for a job, generally, the greater the pay off. Its why doctors are compensated fairly well for what they do (Though the pay for doctors continues to drop while medical school costs continue to increase). It takes a minimum of 12 years after highschool to train a basic primary care doctor and ~250k dollars on the part of the training physician to achieve that goal. This doesn't take into account the cost prior to medical school or the cost and time required post medical school to specialize, say in surgery, urology, oncology, etc.... Plus doctors are in high demand (everyone gets sick) but there are so few of them due to the difficulty of the training, time required, and cost.
Hope you don't mind the medical example, its the field i'm most familiar with.
God bless,
Alex