In all of them, I would change "paid a far higher salary" to "paid too high a salary", or "paid a disproportionately high salary", or simply "overpaid".
"are paid a far higher salary" sounds a little strange because there is no reference point to compare it with.
Also, I would pluralize "contribution" since making aany kind of contributions is usually not a one time thing.
Here are comments on the individual sentences.
3].If it is considered that a person's earnings are measured based on the relative contribution to the society, artists are paid a far higher salary.
=> I would prefer: "If (we/you) consider that ..." or "Considering that ...". It's shorter and clearer.
5].If a person's earnings are measured compared to the relative contribution to the society, artists are paid a far higher salary.
=> "measured compared to the relative contribution" sounds confusing. "measure" is already more rigorous concept than "compare", so "measured compared to" doesn't seem right. "measured by", "measured in", or "measured in terms of" would all be better.
6].If a person's earnings are measured in terms of responsibilities, carrying out the workload and the relative contribution to the society related to their profession, artists are paid a far higher salary.
=> What comes after "in terms of" are similar things worded in a complicated way - they make the sentence lose clarity. I would simplify it to "their professional achievements and contributions to the society".