Generally speaking, they are a little more expensive than conventional plastic and less than some very hi-index materials. You may have a look in some online shops such as local Sam's Club, Costco or Wal-mart. As far as I know, polycarbonate lenses are $74 there for both lenses and include UV, scratch resist, non-glare. Hi-index is $117 with the same coatings in the Sam's Club. It is better for you to check by yourself and you need to take into consideration your own personal needs when you choose one.
Because the polycarbonate glasses lenses are durable which are not easy to be broken when falling down, they receive a lot of people's welcome. However, the price is just suitable. And different stores offer different marked price. You can go online and have a look. The price there is relatively cheap when compared with those in franchise store. And the walmart is the suitable place to go.
It depends,different stores have different price. but I think they are not too expensive. However, you need to take into consideration your own personal needs. If you are in an industry where they may become scratched easily, they are not the lenses for you. If you are in an industry where you may have the risk of getting hit in the face, or have things hit your glasses, they most definitly are the lenses for you. They are the most impact resistant lenses available.