Sure, if the money generated by their image rights and associated sponsorship to the club, along with their overall performance on the field contributing to continued success for their football club then yes they are worth the salaries they are paid.
If however, their salary is not recompensed by the above stipulations then, no.
The value of an individual financially is directly proportional to the wealth created by that individual.
Just stating No doesn't consider the money generated by the individual concerned, who should profit, the club/shareholders or the person responsible for the wealth generated.