Fraud is defined as an [overcharge] of four out of twenty-four silver coins per sela, a sixth of the purchase value. For how long may the customer return [the merchandise]? Long enough for him to show [the item] to [another] shopkeeper or a relative [to confirm the value].
Rabbi Tarfon ruled in Lod that fraud is defined as eight [out of 24] silver coins per sela, a third of the purchase value—and the merchants of Lod rejoiced. He told them, but [the customer] has all day to return [the merchandise]. They replied to him, “Let Rabbi Tarfon leave us as we were,” and they returned to the Sages’ policy.
The Sages define fraud as an overcharge by a sixth (about 17 percent) of an item’s market value. Rabbi Tarfon gave the merchants much more leeway by defining fraud as an overcharge of a third (33 percent). But the merchants’ celebration dimmed when they realized that he gave the customer more time to research the transaction and retract it if he was overcharged. It is interesting that the merchants seem to have had some latitude about which policy they could follow.