Hum, I have never heard about a pair of good fashion designer sunglasses will only take $150. If you know where to buy them, please let me know. I know that designer sunglasses are often very expensive. Though the cost of this kind of sunglasses is a little expensive than other sunglasses, the companies also make a big profit from them. But we can't deny that they are elegant and with excellent quality.
You can buy a pair of designed sunglasses on ebay. And there are some suggestions for you to consider before placing an order. You can have a look at http://www.ebay.com/gds/HOW-TO-BUY-DESIGNER-SUNGLASSES-ON-EBAY-/10000000015747326/g.html
There are many kinds of designed sunglasses on ebay. You can have a look at http://www.ebay.com/bhp/designer-sunglasses. Most of them are really very cheap. They are less than ten dollars. But I suggest you have a good look first. I am afraid that they are of poor quality. So I suggest you to consider the quality of the sunglasses as well. Hope this helped!