[sirsinsalot]

Do you mean crown glass? High index glass? Polycarbonate?

What grade of scratch? What about cost to replace vs non-resistance? What about the average lifetime of glasses vs cost?

By cheap do you mean take less stress before fracture? How about actuations before failure?

See, you don't know. You're just ranting. Yes, you would need to you know ... at least cite some specifics and evidence beyond your own experience. That's how these things tend to work.

[wyclif]

This is just meaningless overqualification, as if you're trying to escape reality. Any kind of glass is going to be more resistant to scratches than plastic, even the kind that claims to be scratch-resistant. By cheap hinges, I mean they take less stress before fracture and fewer actuations before failure.

This is really not rocket surgery. We're talking about sunglasses. As I said above, I don't need to write a white paper or do an academic study to know this is true, it's based on my experiences wearing all these different types of sunglasses over decades and observing how they are constructed and how they respond to various types of normal wear to outright abuse.