Bava Metzia 51: Ways Around Exploitation/Ona'a

Although today's daf continues the rabbis' discussion of ona'a, exploitation in business matters, we are also offered examples that help us to understand the reason for these rules.  First, we are offered stories of people who either over or undercharge someone in a business transaction, leading to an ona'a.  But might there be a way to get around these rules?  The rabbis consider transgressing Torah law in order to settle these claims.

A new Mishna teaches us that both the buyer and the seller; a layman and a merchant, are obligated by the halachot of ona'a, exploitation.  Rabbi Yehuda says that a merchant is not obligated by the halachot of ona'a because he is an expert at determining the market price of merchandise.  The person who has been exploited is at an advantage, because he is the one who can say "Give me back my money" or "Give me back the amount that you gained by exploiting me".  

The Gemara first considers the possible meanings of "you shall not exploit your brother".  Certainly this does not distinguish the buyer from the seller.  So how could Rabbi Yehuda believe that a merchant is exempt from the halachot of ona'a?  

Some possible reasons: perhaps the merchant is a trader who knows the value of merchandise.  Perhaps the merchant is has sold the item at less than one-sixth its value and so no ona'a is required.  

But there are other things that the rabbis disagreed about.  One of these is whether a person can agree to a sale only if the halachot of ona'a do not apply to that sale.  Sneaky!  The rabbis compare this with a man who attempts to betroth a woman on the condition that he does not need to provide food, clothing, or her conjugal rights.  Rabbi Meir ruled that they are betrothed but his condition is ignored.  However, this is a matter of personal obligations.  Monetary matters might be subject to different exceptions.

Does it make a difference whether or not a person knows her/his rights and waives those rights willingly?  The rabbis argue about this point.  Further, they debate whether or not this is an "ordinary case" where the over or underpricing of an item has not been mentioned.  Before introducing a new Mishna, the rabbis also speak to different ways of determining the value of an item and the payment of a porter (someone who delivers the item).  

A new Mishna is begun (but not completed in today's daf).  It tells us that a dinar will erode over time, and that we must determine whether or not a sela has lost its value and might create an ona'a.  The rabbis suggest different measures of erosion.   Is it one-sixth of its original value?  Or another measure altogether?