Ebay- Purina coupon

While searching Ebay I found a coupon for twenty, one dollar off fifteen cans of Purina cat food. I thought that this coupon was funny because it will only save you one dollar if you use it and you have to buy fifteen cans. The seller says that his coupons are free, what you are paying for is the labor it took to collect, cut, ship, and sort the coupons. The bid is currently at $2.69.... I don't understand why anyone would pay for this, you get the coupons when you buy the product. Plus who buys that much cat food at one time.