That rational basis you're looking is called morals. We owe things to each other, although you seem inclined to believe otherwise, and are pushing what is obviously a callous and simplistic version of our society.

I will not continue to argue with you though as this argument is not worth considering any longer.

If people were paid their marginal product, no company would make money. If you pay someone the amount of money they bring to the company, the company would make zero additional dollars by employing them. We are paid based off how hard it is to replace ourselves, not the value we bring. Say x is marginal product, y is the salary someone is paid, and z is the salary to minimize replacement. Every efficient job is x>=y>=z. Fairness is when Y is as close to X as possible. It is fair to get paid as closely to the value you bring as possible, but the market often creates y that are closer to z.