You could also look at local optical shops or camping stores to compare prices. For sunglasses, just as with shoes, and bikes, try them on before you buy. Everybody's head and face shape is different. Different styles fit differently, and look different. For protection from UV, wind, and foreign objects, you don't have to spend much to get a pair that works.

However, you really do get what you pay for in sunglasses. When you spend more cash, you'll see the build quality increase, such as better materials used to make the frames, and better lens coatings. Also, some of the more spendy brands, like Bolle, Rudy Project, Oakely, Native, and Smith have breakage replacement policies of some sort, meaning that if you break your high dollar frames, they charge you only a fraction for replacements. I went through 3 pairs of $30 Performance brand sunglasses ($90) before I realized Natives were much higher quality, and had a replacement policy when they break.