I find the addage, you get what you pay for, applies 80% of the time. I have to get prescription for my poor distance vision so I get prescription sunglasses as well. Employer subsidized medical plans help tremendously. My last pair was Ray Ban and they were great, still are. My current pair that I just got last July are Maui Jims, man are they expensive or what, but they are fully guaranteed and they are the best I have ever worn over the years I have worn precscription glasses. I would not go back to cheapos after the Ray Bans & Maui Jims especiallly the MJ's. I also keep all my glasses, regular & sunglasses on a floating croakie when anywhere near the water. I have had occasion to successfully retrieve glassses that went overboard but it has been a while since that has happened and I am very carefull with my current glasses as both are quite expensive and they do happen to be designer frames and lenses but that is just me, I like the high end labels.
Once you lose your vision it is pretty much gone for life, I value and look after the eyes I have since I don't think I'll ever be replacing them. What are your eyes worth to you?