Money is never made. A friend is only a friend until you sell him something. The sharp knife cuts quickly. Necessity is the mother of invention. Competition and fair play are mutually exclusive.
New customers are like razor toothed gree worms.
His money is only your's when he can't get it back. Never give away for free what can be sold. If a deal is fairly and lawfully made, then seeking revenge especially unprofitable revenge, is illegal. Time is Latinum. Let others keep their reputation.