Is it permissible to demand an increase of ten thousand on the original debt of thirty thousand, after seven years have passed and the business has closed, knowing that the price of the goods today has multiplied several times?

The default rule for repaying debts is with an equivalent amount, not with the current value, and it is not tied to price levels or inflation, unless the currency's value decreases significantly and unjustly. The preponderant opinion in this case is to consider the currency's value if there is egregious deception or a collapse that harms the creditor. Based on this, the lender is permitted to demand compensation for a significant reduction in the value of their debt, whether the valuation is done using essential goods or gold, but it is not a condition that the amount be exactly what they demanded.