The silent millionaires

In a week, at least once I will visit the local night market (pasar malam) with my wife as she shops for her weekly provision. Being a regular, some of the traders there selling their goods are familiar to us as week in week out we see them. Recently I read a book which says that don't be surprised if some of the traders are millionaires. Yes..... you read it right, millionaires! Can you believe it?