[Exhibitman]

I think it is mostly a FOMO and downward adjustment effect. If I see prices soar on nm-mt 1954 Robinsons I am now paying attention, and I may decide to get one I can afford just in case. That's exactly what I did with early Mantle cards in 2015.
Paying off nicely now. Meantime the collectors who were serious about owing one before--doing a player run, doing a 1954 set, etc.--are now going to move on it. Can't afford the 8? Buy a nice 6. The sellers, meantime, are thinking "Hey if the PSA 8 is worth $6,000, why shouldn't a PSA 3 sell for $400?" I'd even think that you could argue the three should sell for $600 or more--why not 10% of the 8 price, if that card stabilizes in that price range?