Bava Batra 92 - Implied Warranty
Normally, the law follows the principle of majority, assuming that the situation at hand is typical of the majority of such cases. However, in money matters, there is another principle: "To extract money from his fellow, the burden of proof lies with the claimant," which trumps the principle of majority. Since the buyer cannot definitely prove his claim, the seller does not have to refund the purchase amount.
Art: At the Market Stall by Louise Moillon
