As a performer, I'm not that concerned about sales. I care much more about the audience's experience. If that experience is disrupted by rude and inconsiderate people videoing, texting, etc then I think it's the venue's responsibility to do something about it.

Seems to me that if an audience member persists in behaviour that is against the rules (couldn't think of a better word) and the rule was stated before the performer took the stage, that audience member should be asked to leave the concert and not receive a refund.

Just my two cents.

Deb