First of all ma'am, you're paying for the convenience of having clip-ons with your glasses. The company that sells those clip on sunglasses/glasses (most likely imf) does not sell the clips individually, and the frame must be sold completely. You're lucky that 50% discount was extended to you, at least you know how much you saved.
Secondly, it does not cost pearle two dollars to make the glasses, that's ridiculous. Lenses are expensive, the store has to pay for the frame, and then they have to pay shipping to get all of it delivered to the store. Before making a complaint, make sure you're well informed. I work for a pearle, and your complaint is certainly un-informed.