> If I can see how much my employer pay others

Then your salary will be decided by lowest common denominator. Employer does not leverage this situation, employer reacts to the incentives this situation creating.

> Then your salary will be decided by lowest common denominator.

Why would it? That's not what happens in practice, and you have raw data to point at, with things like "Person A is half a fast as me, and earns X, that's why I deserve X+N", not sure why you think there would be another outcome here, and it's clear you've never experienced this sort of environment yourself.