Maaser Sheni, Chapter Five, Mishnah Four
This mishnah deals with the procedure for redeeming fourth year produce. How is the value of the produce evaluated?
1) How does one redeem the fruit of a plant in its fourth year? The owner puts down a basket in the presence of three [people] and says: How many such baskets would a man wish to redeem for himself for a sela on condition that the costs [to produce the fruit] shall be on his house?
2) And then he puts down the money and says: Whatever shall be picked from this plant may it be exchanged for this money at the price of so many baskets for a sela.
Section one: In the presence of three people, who will acts as estimators, the owner puts a sample of the produce to be redeemed into a basket. He then asks how much a person would redeem for himself the produce in the basket, under the condition that he would have to pay for the costs involved in growing the produce. We would term this profit. This is very important: the owner doesnt redeem the produce at market cost; he only pays the potential profit. This is why three people are needed to do the estimate. It doesnt take three people to figure out how much something costs at the market. What is more difficult is figuring out how much it would have cost to grow the produce.
Section two: Once we have figured out how many baskets of produce can be redeemed for a sela, the owner puts down a sela and says that the sela will redeem however many baskets of future produce were determined.