I'm a bit of a connoisseur of sunglasses. I'm not a freak on shades but I'm into them to this extent; I own a couple pairs of Oakleys, one of which has four interchangeable lenses and I own a pair of Maui Jim's. I bought my wife a pair of Maui Jim's. Back when Sunglass Hut was a public company, I owned stock.
So, for what it's worth, I recently stumbled across the best value I've seen in sunglasses. The glasses are called Tifosi. They cost 50 bucks and you get four exchangable lenses, dark, rose, yellow and clear. The optical quality is simmilar to Okley's Irridium line with only the rose being not quite as good but the yellow being better - although quite different.
Basically comared to similar Oakley's you pay less than half as much and you get multiple lenses. On me they look nicer too. The baseball and golf Oakley's sit a little too high on my face. The Tifosi Slip model fits just right.
Disclaimer: I have no financial interest in the Tifosi Sunglass company.