I don’t think it’s written in stone how much any given thing should be worth in money. It more like written in history in that the monetary value of things has been passed down through the generations by infinite negotiations, bartering and arguing, cases being made, supply and demand etc - market forces in other words.

However, this means that the monetary value of something is always subject potentially to change if the forces for change are determined and powerful enough to bring it about. When a particular faction in society comes forward to argue for more money it is often done as if from a moral basis e.g. the poor old employees being exploited by the wicked old employers. Of course just as often the employees are as wicked as anybody else and their case will usually be determined by position and power, not by moral superiority.

We should remember that the pure Marxian position was not a moral argument but an attempt (albeit so far a failed one) at an objective and scientifically sound analysis of humans and their socio-economic environment.