Stein Optical I thought had it cheap, though I don't know if there chain is nationwide. I used to go there, but now I prefer a privately owned place, their not badly priced at all, and it's WAY better than any chain stores.
I had problems with my contacts because they kept ripping, so I asked my doctor what I was doing wrong why they where ripping, and he told me why, and he even replaced all the one's that ripped when I didn't even ask, and my contacts are not cheap. You get a lot better service with a privately owned place, and it's worth it.