Error cards go up in value if they are corrected, effectively turning the error into a short-print variation, in modern terms. From there, value depends on the rarity of the error. Back when they’d print thousands of each card, if errors were caught early on in the print run relatively few copies got out, and that scarcity would drive value.

 For example, the “Craig” Nettles error was a big deal at the time. Nettles played for the Yankees who were on the rise again, it was Fleer’s first year, and he was an All-Star level player. Misspelling his first name on the card front was an obvious error of a notable player, and it was fixed early on. That made it worth about $20 at a time when brand new cards of the top players sold for $2 out of 50-cent packs.

The print runs today are relatively small and while there are still plenty of errors, they generally aren’t corrected. When all cards are the same, there’s nothing to drive value.