If I take out a $10,000 loan, which for simplicity's sake let's say is worth 10,000 loaves of bread, and next year, when payment is due, $10,000 is "worth half as much" ie I can only buy 5,000 loaves of bread with it, I only have to pay back "half the loan". I still pay the same $10k, but at the time I paid it back, I only had to trade half as much bread (my storage asset of choice) for it.