Be creative ;) have fun and think about the customer.
If somebody purchased an identical product for $9 instead of $5 it could be location and possibly the customer appreciates buying locally and supporting a local company than purchasing paper at a cheaper rate online where they can't build a relationship with the company.
This is a classic question to ask a Sales candidate, as it weeds out those candidates who can sell "value", from those who rely upon selling "price." An effective Sales professional, will sell the value of a product or service, and successfully close a sale, when value is aligned with a customer's pain-point[s], and provides a solution to a customer's need. One must look beyond the proverbial price-tag, and identify the value-adds of a said product or service offering, and how it provides an effective solution to customer need. In this case of seemingly identical paper products, value-adds to consider could be, reduced order fulfillment timeframe, product availability, exemplary customer support, a more flexible/convenient order/payment process, etc.
I was not prepared for this question but responded that it was the teamwork and high achieving driven characteristics she was looking for. Turns out its more of an individualistic job where you work with other team members to serve the agent.