The Wealth of Nations

In Geneva, bus ticket machines don’t give change back. People having to buy a 3 CHF ticket have to put in a 5 CHF and therefore lose 2 CHF if they don’t want to risk a 100 CHF fine.
However, the city transport agency also sells debit cards with 11 tickets for the price of ten. Most people don’t bother. Others saw an opportunity to make money.

They wait by the machine with cards and a bag of change. When you arrive short of change, they sell you the ticket at its regular price (3 CHF) and give you change. They make 3 CHF per 11 tickets sold (and even more when they cumulate fidelity points and other free tickets).

It surprises me that some people do not see it as a win-win situation. While we get change, they make money. This is what Adam Smith had in mind when he said that, “by pursuing his own interest [a merchant …] promotes that of society more effectually than when he really intends to promote it". It’s the principle of commerce. Furthermore, this process generates value: the surplus earned by the entrepreneurs would not exist if not for this business. Also, we avoid to redistribute money to the transport agency. This is how entrepreneurs make countries richer.