This is how you cheapen a product.
It's why Maui Jim pulled out of Lenscrafters- they don't need the 'volume retailer' just so that that company can do unauthorized discounting on a product worth its price.
I can tell you for sure that Eyemart (similar, not the same) sells whatever massive amount of older PALs are handed off to them just like their disco frames. Until proven otherwise, I will assume the same for Costco.