1. A person should not deviate from the way grain is customarily measured and sold in his area.
2. Beis Din should appoint a person to ensure that the weights used by merchants in their city are accurate.
3. There is a dispute about whether Beis Din should ensure that merchants are not selling basic goods for a large profit.
4. Rebbi Yochanan ben Zakai felt that it was difficult for him to talk about tactics that dishonestly benefit buyers or sellers.
5. The Beraisa similarly discusses forbidden underhanded tactics in weights and measures.
A BIT MORE
1. For example, in a place where the custom is to sell an exact measure and not a heaping measure (extra on top), one should not sell a heaping measure for extra money.
2. This person should also be given authority to punish those who are found to have faulty measures.
3. Shmuel: This is unnecessary; competition will cause merchants who need money to lower their prices. Karna: This should be done, as there are dishonest merchants who will price gouge.
4. He did not want a dishonest buyer or seller to hear that he forbade a tactic that would give an advantage to the buyer or seller, as this might give him the idea to implement that tactic in his business. On the other hand, he could not be silent about these matters, as dishonest merchants will think that the sages are not aware of their trickery.
5. The Gemara continues and says that a person may not have a measure in his house that is inaccurate (even if he does not intend to use it for sales), as he might use it to weigh something he is selling.