Once a slabbed chip has been bought to the market and sold, it will be replaced by another slabbed chip to be sold.

How can/do you know that? I remember many more slabbed chips offered up for sale on eBay 5 years ago. Today it is a rarity. By your logic, we should see at least the same amount being sold, and it is CERTAINLY less.

Why?

Because of what I stated earlier----a seller would be a fool to knowingly list slabbed chips. He is cutting his potential market drastically.
And as for "recent" slabbing activity, I can't really answer that, but I can guess, and my guess is there has not been a significant newcomer to slabbing recently. There would be a buzz here. When was the last time the Slabfree crew added to the "list"? Again, I don't know for sure but I would be surprised to learn if there were substantial additions recently......save this seller!

It is dead, save for the rare "OHH look what this seller is doing on eBay posts" you see here. Chart the number of those posts and you will see that number is alot lower today too.