Errors increase the value of collectibles because a limited number go into circulation before it is spotted and corrected.

There are coins and bills in circulation that can be sold to collectors for thousands or even millions of dollars. The better their condition, the higher their price. This is the case for certain US ...

https://siris-libraries.si.edu/ipac20/ipac.jsp?&profile=liball&source=~!silibraries&uri=full=3100001~!304041~!0#focus ...