people who don't have a coupon. When a store does a coupon, they only give the coupon discount to holders of the coupon. Is it unethical for the store to charge all the saps who don't use a coupon?
The buyer has the burden of asking for and getting the best price. And the seller is doing the same. I don't know what kind of weird ethical line would make selling a product in this situation unethical especially with no duress.