There are 4 major bumps in a cards value:
1. Rookie hype
2. Performance jumps out of seemingly nowhere by "nobodies" like Tage Thompson. But these bumps dont usually end up with incredibly high valuations since their cards started out so low.
3. Cup wins
4. Hall of Fame.
Mvp awards usually see minor bumps for a ahort time, but nothing spectacular
#1 sets the tone for 3 and 4. If a guy is looking for home run card selling... have to get them when they're rookies and see ideally both 3 and 4 down the line, along with a high grade... 9 or better. Also depends on which company dies the grading since PSA just gives blanket numbers as like 8, 9 or 10, but Beckett gives 4 separate grades for corners, face, centering and edges. To get a true black label 10 grade from Beckett is exceptionally rare, very much by design of course.
Missing #3 doesnt mean a HOF talented players card value will suddenly get cut in half. Market variances exist of course where people will sell for cheap for any number of reasons, but no HOF players cards value craters because they dont win a cup, they just wont go up as much.
If they miss 3 and 4, a d all they had was the rookie hype and a decent but not great career, yeah they could go down a bit.
There's very few cards though that have the kind of rookie hype around guys like Matthews, Crosby, McDavid, Ovechkin, Bedard etc. Won't be again for a while it looks like.
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