The market for sunglasses

Many famous brands have sunglasses as part of their product line. Many sunglass manufacturers also tout the features and special textures of their products. Depending on the feature and brand, sunglasses can range in price from less than $20 to a few hundred dollars.
Plus, there will be imposters out there. When you visit discount stores and flea markets, you'll find vendors selling knockoffs of expensive brands of sunglasses that look identical on the outside, but cost far less than the real thing. When you buy those genuine brands of sunglasses over the knockoffs, are you paying a lot for just one brand, or is there a real difference?
The biggest problem with cheap sunglasses is the way the lenses are made. They are simply coated with a coloured film on top of ordinary plastic. Even though the colors and frames of these imposters resemble those of some famous brands, the actual lenses are quite different.