It is the price divided by the surface area. It is used because it is the only thing that allows us to compare a property of 200 hectares with one of 3,000: the total price says nothing by itself.
It is usually quoted in dollars, for the same reason that almost all real assets in Argentina are priced this way.
The factors that drive it the most are land capability and productivity index, the rainfall pattern, the distance to port or grain elevator, the state of the roads, and legal restrictions. The saline impact and the category of native forest can change it drastically without being seen on a tour.