A very good question. It seems from different Sugyot (Kiddushin, BM and more) that a $1000 worth of good land is perceivably worth more than $1000 worth of worst land. For example, אחים שחלקו - brothers that inherited land and seemingly divide it by its value might have additional considerations, not strictly assessable in value and therefore they are allowed to break the deal later.
A possible reason for that is (my own conclusion) that in their times they had very little flexibility in prices, and the price did not reflect additional considerations. This is consistent with the Sugya of Ona'a - how come that different tomato are sold in the market for the same price? So they had a price list with only 3 types of land, however, the "best land" had many additional circumstantial benefits not assessed in its price, like proximity to water sources, easy access, easy to trade etc. and more.
An additional example would be paying a $1000 debt with $100 or $1 bills (as the Gemmorah claims that the debt could be returned with crops). Even if that's the same monetary value, one is perceivably valued more.
So paying with the best land does not pay the exact amount of debt, but losing additional benefits not included in the price.
It should be noted that nowadays we tend to assess the value taking into considerations all possible pros and cons. it reminds me that some 20 years ago, here in Israel, the semi-official price list for a car only included the model and the year. Today it has more than 10 additional features, like types of previous ownership, mileage and more.