Leviticus 25:15-16
15 You are to buy from your countryman on the basis of the number of years since the Jubilee. And he is to sell to you on the basis of the number of years left for harvesting crops.
16 When the years are many, you are to increase the price, and when the years are few, you are to decrease the price, because what he is really selling you is the number of crops.