[beambot]

Lollipuff (YC W'13: https://www.lollipuff.com/) does exactly this for higher-end women's fashion -- to directly address the issues you had with your Tiffany necklace (though I don't think they support Tiffany today). All the items get authenticated before listing by professional authenticators, without needing to take items in hand. This provides more-than-ample evidence in the event of a dispute (the authenticators are well known in the field!). Then Lollipuff walks buyers & sellers through the process to ensure a safe transaction -- including instructions on shipping, which can also be a frequent gotcha for high-end items.

[ssharp]

I wonder how much eBay has been impacted by this type of "wedging". I would use eBay primarily to buy/sell musical instruments but Reverb took a pretty big chunk of that market and provides a better and more trustworthy experience than eBay, at least in my experiences there.

I know there are a few fashion-related sites like this out there and I'd guess there are other "Reverb for X" sites as well.

I'm sure there is still a fortune in the long-tail but specialty sites seem to be more of a concern than a direct competitor.