I wonder to what extent the presence of insurance in the mix has made things worse. Markets never work particularly well when the entity paying and the entity choosing the product aren't the same. Textbooks (vs normal books) come to mind as an obvious example of this.
Anecdata being what it is the last non-Zenni glasses I bought were from Lenscrafters and had a blurry spot they refused to acknowledge or fix and I lived with it for years.
Zenni glasses are so cheap if you get a bad pair you just buy another.
Can't comment on weight differences and so on. I haven't had a problem with the weight of the lenses w/my prescription. My wife has a very strong prescription and purchases the highest index option and she hasn't noticed a difference. Index is index and material is material so unless you are comparing apples to oranges is it actually possible for them to differ?
Regarding clarity. I get more mileage from cleaning my glasses with dish soap then I do from the optical qualities of the lens. Maybe mine get dirty faster then most.
Categorical and plain wrong —
Have had these glasses for more than a few years, have sat on them, dropped them on concrete, etc. Still going strong.
Luxottica may be overcharging, but truth is the discount brands do not carry a comparable product. Certainly you can save money at those places, but the product isn’t the same. In some sense you are getting what you pay for. You can get even better lenses from Zeiss and Nikon if you go beyond Lenscrafters, but I haven’t walked that path yet as it’s a bit beyond my budget (read: insurance), although I’ve heard excellent things.
Edit: Grammar.