Of course you don't have to spend a lot of money, but don't think that you get the same quality lenses for $12 as you get when you pay more. I have several different pairs of polarized sunglasses and the Ray Bans and Bose Sport ones have far superior optics in the lens than the $15 pair I got in a 2 pack at Costco.
In addition, my Ray Bans have large, wrap-around frames that COMPLETELY block out light bleed from the top and sides, which is essential for me on sunny days outdoors due to migraines. I have not found a comparable fit on cheaper sunglasses. Plus, the Ray Bans are a much darker tint with a greenish cast that also helps prevent eye strain by reducing glare and brightening shadows in all lighting. Again, you won't find that in budget sunglasses.