There exists many “groupon” type site in which you buy a gift certificate to a store at a large discount. Part of the reason for the sale is to attract new customers and part is that the store gets cash up front. Does that pose a ribbis problem as you are getting a cheaper price for buying ahead of time?
This will not be a problem of ribbis.
The problem of ribbis arises only when a store offers two prices, one price for cash up front, and another price for payment in installments. This is not Torah ribbis, because it remains a sale, but it involves a rabbinic prohibition on account of the clear discrepency between cash up front and payment in installments, which makes the more expensive installment payment look like ribbis.
In this case, there is no “cheaper price” being offered for cash up front, and the sale of the gift coupon will not be considered as offering two prices, because it is not a sale price for goods but a separate purchase of coupons. This is true even though one of the motives might be the gain of direct cash payment.