That's one sort of "fairly" - that employees should participate in profit sharing and that their compensation should be tied directly to the value they create (

That's one sort of "fairly" - that employees should participate in profit sharing and that their compensation should be tied directly to the value they create (though should employees also share in the losses?). Another kind of "fairly" is that Labour is its own market, and employees should be paid commensurate to their replacement cost. Both are valid models, though the latter is much more common. The difference between which model is followed can often come down to the negotiation abilities of the individual employee (or their agents) and their relative scarcity. E.g. an extra for a hollywood blockbuster movie is paid the same daily rate as an extra on an independent art-house film - because it's easy to hire extras and they are interchangeable. The movie stars on the other hand are more scarce (at least those with marketable reputations are) and so can negotiate points on the gross.