This practice is illegal. It's like having a relative that works in a store and when you come through the line they ring up a dollor instead of a hundred dollors. I was in a store, it was a Zayre store that has since gone out of bussisness many years ago when a casher and the person in line was arrested for this practice. The situation here sounds like a vengful act but none the less is prosacutable if intent can be proved. I personally couldn't screw the owner like that after I found what the truth was. Do the right thing.