People often assume that a low print run automatically means a card should be worth more, but that is only true when scarcity and demand meet each other. A card can be rare and still be cheap if nobody wants it, and a card can have a healthy population and still be expensive if the player or set is heavily collected.
Print run and population are not the same thing. Print run is how many were made, population is how many were graded and verified. A card can have a tiny PSA population only because nobody bothered to send it in. True scarcity is proven either by a documented low print run or by years of consistently low supply in the wild.
The safest way to think about rarity is to start with demand, not the serial number. If the player, set, or insert line is already collected and respected, rarity amplifies value. If the player has no following, rarity just means the card will sit in someone’s box unsold. Value is created by interest first, scarcity second.