Those who say that interest is forbidden (and equating usury to it), please answer the following question with your Islamic reasoning:
... your friend lends you $1, in 2005 (an amount which could purchase 1 can of coke at that time), with mutual consent between both parties that you will return the sum in one year. However, you fail to return the due amount on time (in 2006), and decide to do so 25 years later, in 2030. Due to inflation, a can of coke now costs $5, meaning that the value of $1 of 2005 is now (in 2030) equivalent to $5. Will you pay your friend back $1 or $5?