I was in a used bookstore one time, a guy came in with a book he found was about 130 years old but was disappointed when the dealer told him unfortunately the author is an unknown person and book has no value.
I bought a 1906 American silver dollar from a guy in a bar once for $20. Coin dealer said no thanks has no value because too many were minted and no demand.
The value of an item is based on what the buyer is willing to pay. However, if an item has emotional value then usually it is priceless.