Worth What People Will Pay

My father always told me that something is only worth what people are willing to pay for it. Similarly, a person's time and labour must also be worth only as much as someone else is willing to pay for it. So why is the Guardian asking:

Your salary: are you worth it?

If someone is willing to pay it then you must, by definition, be worth it. The only exception, I suppose, would be those employed by the State whose wages are paid for with other people's money.