The price of high index lenses rises up exponentially as the high index rating goes up.Firstly because the material used to product high index lenses is a chemical synthetic blend.The raw material cost, just to produce sheets of the high index glass or plastic used for the lenses, is very high on a production level. Even 1.67 and 1.70, the lower ends of the high index range, cost more than double the price to produce than standard glass or plastic material. 1.74 high index plastic is about three times as expensive, and the high index glass options take another quantum leap forward in raw materials cost. A second factor affecting price is the "wasted material" factor. High index lenses have a tighter tolerance range in prescription cutting than standard plastic or glass. This translates into less leeway for error. Traditional plastic can allow a difference of plus or minus 0.1 millimeter and still fall within guidelines for a particular prescription. High index material will only allow a variance of plus or minus 0.01 millimeter.