Not all old comic books are valuable. Age is perhaps the least accurate indicator of what makes a comic book desirable. Like other antiques or collectibles, value is determined by how much a collector is willing to pay for the item. There are four basic criteria that make vintage comic books appealing to collectors: condition, supply, characters, and story.
Since comic books are intended to be read and not just looked at, it is sometimes difficult to find key old comic books in mint condition. Those that have survived decades of readership are highly valuable. If they have been properly stored, the chances of retaining value are better than if they have been sitting in a box in an attic, although you shouldn’t discount grandpa’s old copies of Spider-Man. Even in average condition, some of the most sought-after comics can still fetch quite a price.
The supply of particular old comic books is important to figuring value as well. Just as supply and demand work for any retail product, the less supply of a particular comic, the greater the demand. If there are 15,000 copies of the comic in perfect condition, it is going to be less desirable than one with only 100 known copies in mint condition.
Books featuring major characters are going to be significantly more valuable than ones featuring minor or unknown characters. Names like Superman, Spider-Man, Batman, Hulk, Green Lantern, Wonder Woman, Captain America and the X-Men among other recognizable names are going to fetch the highest dollar. Issues with these characters are going to be much more appealing to collectors than those featuring the relatively unknown Dartman.
Finally, the Holy Grail of comic book collecting is to find first appearances and other significant events for major characters. The first appearance of a particular character is not necessarily the first issue of their series. Many major characters appeared in anthologies or as characters in other series before they had their own. Other events that collectors find appealing are major life changes like births, marriages, loss of power and deaths. Also of interest are issues of crossover into another series.
Based on these factors, the top 10 most valuable old comic books if in mint condition as of early 2009 are:
1940 Whiz Comics #1, first appearance of Captain Marvel. Valued at $84,000 US Dollars(USD)
1940 More Fun Comics #42, first appearance of The Spectre. Valued at $84,000 USD
1940 Flash Comics #1, a promotional comic featuring the Flash. It is valued at $97,000 USD
1941 Captain America #1, first appearance of Captain America. Valued at $125,000 USD
1940 Batman #1, first comic devoted to Batman. Valued at $125,000 USD
1940 All American Comics #16, first appearance of The Green Lantern. Valued at $160,000 USD
1939 Superman #1, first comic devoted to Superman. Valued at $270,000 USD
1939 Marvel Comics #1, first appearance of the Human Torch and other characters. Valued at $330,000 USD
1939 Detective Comics #27, first appearance of Batman. Valued at $375,000 USD
1938 Action Comics #1, first appearance of Superman. Valued at $440,000 USD