I get access to salary statistics every year via my union. They collect everything from the member, support is almost always around 80%. Just plug in area, experience, title and if you have a management role. So yeah, my answer would be: most people have insight in salary levels.
Also remember that in some countries you income is public record that can be looked up by anyone.
Also remember that in some countries you income is public record that can be looked up by anyone.