For Sale!

How hard is it to understand the following: Buy 2 $20 gift sets and get them for $30...?
Well, apparently it is as hard as learning Korean. A woman and her daughter come into my store and they're looking at our gift set. I proceed to go up to them and tell them that they can get 2 gift sets for $30 if both of the sets are $20. So they come up to the front, one $20 set in hand and then a canister with a pound of coffee. The canister is about $14, the pound of coffee $15. I proceed to tell her that the canister and coffee were not part of the deal because it isn't even a gift set, let alone $20. I get the most confused look from the mother as she meanders over to the giftsets and chooses another one. She then brings up a second giftset and even looks at the bottom before getting to the counter, and hands it to me. I turn it over and it says $25. How in the world is this confusing for her? Her poor daughter looked ready to bolt. After 10 minutes of trying to help her out, she decided to just buy the $20 giftset, pound of coffee, and canister. She walked out of there $58 in the hole. Thanks for being dumb and making use of our deals.