It's wrong to sell things that don't belong to you.
Sue and her housemates are having a yard sale together.
Sue wants to make a lot of money.
Sue puts out a lot of her unwanted items and works hard to sell them all.
Sue sells a book that belongs to one of her housemates.
Sue makes a good amount of extra money for her efforts.
Sue has to buy a new book at full price to make to satisfy her angry housemate and loses money.