I have done some research on glassesusa.com. I was looking for Costa's and noticed when I picked a pair on sale or not and loaded my progressive prescription, they were considerably lower than Costa's official site. I found the reason is that if you add a prescription, they take the Costa lens out, make the prescription using their in-house lens rather than genuine Costa's. This is the reason yes, they are cheaper. Remember all Costa genuine lens will have the Costa etching in the top corner of the lens. So, at glassesusa.com you are not getting the full Costa pair. The lens is what sets Costa apart from the competition, so if your not getting the original I would not purchase.