As far as i know, almost all brands sunglasses are expensive. If you want to get inexpensive brands sunglasses, you can search them online for cheap price. And i noticed that framedirect.com provide some brands sunglasses at affordable prices. In fact, if you want to buy sunglasses for eye shielding or fashion, you needn't buy brands sunglasses. Common brands sunglasses with good quality can also satisfied you.
I am wondering whether you just want branded sunglasses or just normal sunglasses. If you just want normal sunglasses, you can try some firmoo sunglasses. Just search sunglasses at firmoo.com You will find a lot there.