I don’t get this. It is not possible to underpay (when there is no allegation of discrimination) because if a person X is willing to work for salary Y then that

I don’t get this. It is not possible to underpay (when there is no allegation of discrimination) because if a person X is willing to work for salary Y then that’s exactly what he should be paid. In capitalism, corporations have a fiduciary duty to pay no more than is necessary to keep the employee.