There is a lot of hype about sunglasses. I have a nice pair of polarized arnette sunglasses, and a pair of spy polarized that I use and work well The arnette are amber and the spy darker. I've never used a cheaper pair so I can't compare them to cheaper ones. They have lasted a long time (4 years plus). I feel like I can see pretty well below the water.
I'm thinking you should figure out what type of fishing you are doing. If you are sight fishing, or casting for musky I would say that you need a good pair. My brother fly fishes and has several pair depending on light conditions. If he can see a fish before the fish sees him he has a good chance of catching it. If you have no need to locate or see fish than any old pair will do. If you predominantly troll than polarized glasses won't make a difference to you.
Whatever you do remember to always wear sunglasses. As Dave Mercer says, they can save an eye.