Sunglasses are hard to evaluate, except in Tiers. I would say these are Tier 2 sunglasses, with moderately-expensive pricing and yet with performance expectations near Tier 1 sunglasses. Tier 1 would be major brand-names such as Oakley or Rayban, and come with major pricetags (mostly for the name). Tier 3 would be no-name sunglasses, with bargain-basement pricetags. I've picked up noname sunglasses off Amazon for about $8, and for that price, they well exceeded any expectations. Tier 3 sunglasses can be great, with some minor misses on quality, especially in the lenses/optics, and limited colors & styles. Tier 4 sunglasses might be those $1 or free sunglasses you'd give to your young child just for fun.
At $50, I expect a lot more performance from these, and they largely deliver. The lenses/optics are polarized, and provide good sun protection and clear vision even in near-direct sunlight; in this way, they're a step above Tier 3 sunglasses. I prefer to wear these over the high-quality Tier 3 sunglasses I own, specifically for the quality optics/lenses. The frames, themselves, straddle a pleasant middle-ground between soft-touch plastic and hard/cheap plastic; they feel just right. There appear to be fewer available styles than I'd expect at this price point, but they are all interesting and fashionable.
The accessories are fair. I've had better pouches and cleaning cloths from Tier 3 sunglasses offerings. I don't know what I'm going to do with this elaborate box. I'm sure I paid for it with the $50 pricetag, but it offers little long-term value. If you're like me, you'll *want* to save it since it looks nice and since you paid (a lot) for it, but eventually it'll gather dust on some shelf and wind up in the trash being unused for years. I'd prefer to be more environmentally conscious, and perhaps have saved a few bucks, and done without the fancy box.
The major differentiator between these Tier 2 sunglasses and the $8 Tier 3 pair is the warranty. I didn't see it listed on Amazon, but I found on their website that Black Sail apparently offers a lifetime warranty as a one-time replacement.