I don't know about that on parts, I have a few extra parts and in past years they were easy sells. Now in the last year or two they aren't, so I guess I will just stash them until the market comes back.
While gathering parts for a Challenger project 5 years ago, mint unpitted or NOS side marker bezels were about the hardest thing to find. I have paid close to $200 for a nice assembly and I even saw people asking and selling just the NOS lenses for over $100! I'd bid on NOS assemblies on ebay but always got outbid, 1 NOS assembly would bring $450!
Last year a NOS front assembly turned up on ebay, I bid on it for laughs and grins, and lo and behold, ended up buying it.... for $137! That's around what just a NOS lens could be sold for 4 or 5 years ago.