Compared with the common prescription lenses, the 1.74 index lenses will offer the thinness. In addition, the refracted light rate is better than the common eyeglasses lenses. However, the price of 1.74 index lenses is relatively higher, charging about $ 200. But they are worthy the price for the ones with high prescription.
It depends on where you buy it. The prices of 1.74 high index lenses are different at each shops. But what i can tell you is that such high index lenses are expensive. They usually sold at a higher prices compared with regular index lenses. As far as i know, The 1.74 Aspheric lenses are sold $110.00 at firmoo.com. Hope this help.