I had to do a total double-take there. That has to be the weirdest metric of a product I have ever seen.
I will also add that any laser safety glasses that cost $3.18, can’t even protect you from looking at a photo of a laser, let alone a laser for real…
Oh, and before @Dan jumps down my throat, that is NOT safety advice, since these are for cosplay, not for the GF, but it is a comment on likely quality of said items…
As far as I am aware all glasses with lenses in them that aren’t zs will protect you from CO2 lasers. Not sure why you have to pay extra for them special glasses. (I have some just in case lol)
You are probably paying for testing / certification / traceability and much lower volume production and sales necessitating a higher profit margin.
And maybe a bit higher manufacturing cost, and probably insurance premiums. (There was a time when it was reported that roughly half the price of a new general-aviation aircraft was insurance, although that was mostly a result of previous mispricing.)