You maximize your profit as a proxy for maximizing your utility (and some people choose less profit because "helping others" boosts their utility more). Since

You maximize your profit as a proxy for maximizing your utility (and some people choose less profit because "helping others" boosts their utility more). Since we're both maximizing our utility in a free market, it's arguable that the outcome of our transaction is maximum fairness, or at least a local maximum of fairness.