You don't have to spend as much as the cost of Oakleys to get good sunglasses but if you think you are getting the same thing for <$10 you are kidding yourself. Yeah they may be tinted but that doesn't mean they are protecting your eyes at all. Now your pupils are dilated from the shade while all the harmful radiation from the sunlight is going straight in...

http://science.howstuffworks.com/inn.../sunglass1.htm