incidently, when I worked at the opticians, we never tried to compete with Tesco or Speccy****s on price. We couldn't hope to. We used qualified staff that cost money and we didn't have their buying power. We instead competed by offering a better service and higher standards. People came to us not because we were the cheapest, but because we were good, and we did well (the folks have now sold the business and retired). After I finished there I went repping for one of the biggest suppliers in the UK. Of the Opticians I visited the ones that were doing well were doing the same. The ones that were trying to compete with the big boys were in a state of perpetual financial collapse.
Try and compete with tesco and their ilk if you like, but personally I think it's the road to financial ruination