I agree with you, I don't think gray mop is rare to begin with and setting things in pink gold doesn't make it THAT special.You are correct about materials availability.
My position is simply that considering the fact that LE earrings have never been offered before (unlike pendants) it would have been truly special to see a stone that has never been used before (such as chalcedony or gray mop) in a vintage earring.
Onyx is a very common stone and odds are many of us already own the vintage onyx earrings. Same applies for white mop. I don't feel that the fact that they are set in pink gold makes them different enough (for me) to justify owning them.
As far as raw materials go, gray mop is not all that difficult to procure. In fact, a high end tile company offers it.
I can only see it as VCA being lazy and not put a lot of creativity and thoughts into this 50th Anniversary release. It's exactly the same limited edition pendant recycled and set into ear clips! VCA is probably banging on purchasers of last year's pendant shelling out more $ for the matching ear clips!