Do you think if a performer is willing to undercut you [and you know this for fact] said performer is also willing to undercut others? Do you think people should be made aware of this since it could potentially cost them a paycheck? How would you proceed?

I am not sure how to proceed. Could it be that this performer believed they aren't worth the money you are? Perhaps simply telling them what they are doing in case they are unaware. I personally would not be sure what to do.

Ask away...I have little shame and no pride to dent!