There is no way to unambiguosly decide who is responsible for which earnings.

Hipothetical two people cooperative that produces simple hammers. One specializes on wooden part, the other on metal part. How much each of them earned to the company? (Or producing and selling; or one spending his lifesavings to buy pricey hammer-making-equipment while other presses buttons on said equipment)

Goes further than that too, suppose the one working on the wooden part is slow and the one on the metal part is faster. And surely the value of one part or another is also different, even though its the combined value that's relevant.

Suppose as well there are a thousand people lined up to make the wooden part but hardly any for the metal, then surely the ones who work on the metal part will (try to) command a higher wage too.