Is the value of the portion of land against the debt calculated when it is paid to the brother at today's price or at the price of 2019?

It is permissible for the mother—if her brother agrees—to pay off her debt from her land by selling a portion of it to him in exchange for the debt. If the currency significantly depreciates, the more preponderant opinion is to consider the value of the currency at the time of egregious deception (ghabn fahish) or collapse that harms the right-holder.