As for me, those links weren't the website that I saw, but those are good too! This other guy took a perfectly fine (but cheap, old, surely nothing valuable) lens (that may have already had a flaw, I don't recall), and subjected it to increasing damage, and challenged the viewer to tell the difference. It was quite amazing. It wasn't obviously bad until the lens was really banged up! The jist of it is that minor scratches were basically undetectable. Even so, I prefer my flaws to at least be outside the center of the lens. :-/
But yeah, resale is low. But I bought a cheapo "bargain" grade lens once that has slight scratch marks way out to the side, and I have no qualms about using it. It's a fine lens for what it is.
However, since all of this testing is on the front element, that still begs the question of what if there's something on the rear element (perhaps on the inside, like in this new camera I got)? That is bothering me a bit, still.