Earlier quoted context omitted.
Actually, it is how the world works. If there was really a gender pay gap for women who are doing the exact same work as men with the exact same experience as men, then it would be trivial for employers to reduce their costs by only hiring women. Yet, nobody ever does this.
It is true that in a purely rational system, there would be no pay gap (controlling for ability and impact). But guess what...
They care about one thing, dollars. If you are making them money, they will keep you no matter what. If you are not making them money, they will get rid of you. Pretty rational I think.