There are a lot of assumptions required to have that statement be sensical including a lack of transaction fees (including, just, effort - you're assuming the time it takes for you to arrange the purchase and resale is without value) and extreme price stability. 100$ worth of peanuts isn't worthless to someone with a peanut allergy but it is certainly worth less than it is to someone without since to the person with an allergy the only value of peanuts is as a bartering currency.