I gladly paid $800 for my sun glasses. Most of the money is in the corrective lenses. I do know something about the eyewear industry as I liquidated a failed marketer/distributer of branded eyewear. The direct variable costs of my sun glasses is probably less than $50. Realistically, I could not find what I bought for less, as any business that tried to sell for less would go out of business.
First, the cost of the purchase experience. I went to my local optician, who pulled about 50 different frames for me to try on in the process from an inventory of several hundred frames. I picked ones that look great on me, and the lenses sit on the right place relative to my eyeball. Then, my eyes and the frame were measured with a laser for an exact fit. The next day, the owner of the store, not the salesperson who I worked with, called me in, and I switched frames. The style I choose was too "curved" and with my correction, would have caused lots of distortion. So, I went through an abbreviated process again. I will hopefully be able to wear these glasses at least 5 years before I have to change the lens due to changes in my eye and I will be back to the store at least 4 times a year for adjustments. I ended up with Luxxotica made frames under the Oliver Peoples brand. The lens cost about $600. When I check frame for frame and lens for lens, I can't find these for less on the internet and the accuracy of the lenses is doubtful with self measurements. And yes, there is a hug difference in my ability to see with these lenses.
So, for the optician, one sale for 5 years of ongoing service to carry the cost of a retail store lease, 3 to 5 people, equipment and lots of inventory. His is a low volume business that needs high margins to survive.
Can I get this at Wal-Mart or Costco? Absolutely not. I have asked. These stores do not carry anything but 5 year old out of date lenses. The frames are bottom of the line and the color will wear off because they are so cheap. The company I liquidated sold to Wal-Mart and Costco and the landed costs of the frames was under $4.
Can I buy these at a Luxxotica owned chain store? Probably not. The particular frame for sure. Local opticians won't carry something that is sold for less by the same manufacturer. The lenses, maybe, but I doubt for significant savings. Again, when I checked, the lenses at Lens Crafters or whatever the chain is called, were not the most recent technology, but newer and better than what is in Costco. Is Luxxotica making a fortune on all of this? They are doing well but not making a fortune. The styles change constantly and they take back all of the unsold inventory in the stores and in the US warehouses. For a dud frame this might be 80% of production, for a winner 15%. For a brand name, Luxxotica, Marcolin, Safilo, etc., pay a significant licensing fee.
So, you rarely get more than you pay for and $10 knock off are worth only $10. For many people, that is all they want and probably need. Cheap sun glasses, known in the trade as "sun" is the largest market followed by dime store peepers. However, if looking good is important to you, there is nothing like going the process of trying on lots of frames that are selected by someone who knows what they are doing. People look at your face and focus on your eyes so your style in eyewear matters a lot. If you buy new sun glasses frequently to go with the latest style, than my approach is rather costly. If you don't need corrective lenses or only have a mild correction, the latest and greatest lenses won't make much of a difference. However, because sun lenses are much bigger than regular eye glass lenses, distortion is a much bigger problem.