Gold prices are higher now, so I guess some sellers feel that with the branding and all the increases, any savings are good savings.
If it is a discontinued piece, then sometimes they feel justified in raising it even higher.
With tiffany.... I think ebay prices are probably going to be more than what you might pay at a local pawn, depending on where you live.
Like anything, something is worth only what you are willing to pay for it.
I lost a one of the pair of my favorite T&Co earrings. The style was discontinued... the lowest price I found for a preowned pair was $50 over what I paid retail about 8-9 years ago. So, I counted myself lucky.