Bava Metzia 51 - No Price Fraud for Personal Possessions
One man was selling silk ribbons, asking six zuz, although they were actually worth five, and it was apparent that he would take five-and-a-half. Another man came along and said to himself, "If I give him five-and-a-half, it will be considered an immediate waving of the overpayment. I will instead give him six, and then summon him to judgment for the entire overcharge of one zuz."
When he came before Rava for a ruling, Rava said to him, "The rules of overcharging apply only to a merchant, but when buying from a householder, the buyer has no claim of price fraud." People consider their personal effects dear and sell them for more than their worth.