For example

Does this basically mean "Completely forever no-chance-of-return-or-devaluation ever retired and gone?"

Nothing on Subeta is retired forever.

Artifact are items from the MC. (Millionaire Center)

Artifact does mean that it's an item sold in the Millionaire Center so theoretically it can make a return any second. Apart from that nothing on Subeta is gone forever so there's always a chance that a retired item will come back one day. :)

So I've heard. I thought these might be the exception. Thanks.