We can take this further. We can look at any other industry and see a disparity between seemingly 'equal' people where skill level/ability is taken into account before wages are conferred. Teachers, nurses, doctors, pilots to name but a few. All of these people will have - broadly speaking within their own industries - the same qualification as anyone else within their industry, yet can receive vastly different wages based on how good they are at the job.
If we accept that that is true - and, more than true, perfectly acceptable and legitimate - in some professions, why not all?