It’s gonna vary. Some stuff is gonna crater (overproduced modern). Last place I'd want to be right now is holding a stack of shiny crap basketball. Ditto all of the mainstream postwar PSA 7-8 level cards. I'm selling off everything marginal at that level except for the guys I really collect (Aaron, Koufax, Ryan, etc.) or the cards i got when I was a kid. At the depth of the last go-round I was picking up that sort of stuff for as low as $1.99 a card, slabbed. Made really nice profits turning those out during the bubble.
Some stuff won’t budge. A T206 Wagner isn’t gonna fall because the market for it is like the art market: people with so much money that inflation and recession are just gnat bites. Absolute rarities too. A card with a handful of examples will be a hold and you will be able to name your price. As always. I have never been squeamish about those kinds of cards because I know that there are buyers.
The squeeze will be in the middle. Abundant stuff will take a hit. Even the good stuff. I'd guess that a 40%-60% decline is in store for most mainstream cards that are basically demand driven. Personally, I am looking forward to a nice, fat decline on some cards. 1959 Topps Bob Gibson, you will be mine again!
The other thing that won't be affected--that will in fact do well--are cheap vintage cards. The dollar boxes. Collectors need their fixes. During the last one the dollar boxes were where all the action was at the shows.
The real question for me is what is a long term keeper. I think a well curated collection emphasizing top players and rare cards will be a great performer as long as you’ve gotten in well below the peak. Even a marquee card is a bad buy at the wrong price. The question is whether I want to play the arbitrage game with a card by selling it now and hoping to repurchase it after the decline. I am disinclined to do that with cards I always dreamt of owning: to finally get one that presents nicely, I am happy to own it for a decade or more. If it goes up a bunch in ten years, fantastic. I can seem really prescient and smart. If it doesn't, I can play with it until I am food for worms. Either works for me. Owning a great card isn't like taking a position in a stock. I can't play with 100 shares of Tesla but I can sure as hell play with my cards:
