A person himself/herself knows his/her worth. It should not be decided by superiors and in case if they are deciding( in most cases) then they should be just and fair.
But, always they consider they are doing enough for the works ( a common mentality in their minds)
On the other hand, workers are grinding themselves up in the work. So, they should get their pay according to their work and education/standard.
Yeah, it's true. It's a pity that bosses always think like bosses and, most of the time, they're terrible