Ultimately, comic book values are determined by what someone will pay. Some comic collectors think that they should be able to sell their comics at the price listed in their price guide. This isn’t always the case. The value of a comic is a living, breathing thing that changes over time. The price paid will be influenced by things such the person in question — someone who is buying the only issue missing from their collection of a particular series is likely to spend much more than someone with a vague interest in the series. Perhaps the person buying is a master negotiator. That said, there are several broad factors that determine the value of comics:
Action Comics #1 is a good example. According to Wikipedia, fewer than 100 copies are known to exist, and few of them are in good condition. In Feburary a copy in fine condition was sold for $317,200. I wouldn’t be surprised if most of the 200,000 copies of the original edition were destroyed by “loving” parents doing what they do best: throwing comics in the trash. I’m not bitter.
Your comic book values aren’t necessarily high just because your comics are old, even though older comics, generally speaking, tend to be more valuable. You could perhaps argue that it isn’t so much the age of a comic that makes it expensive, as the fact that older comics are rarer. I thought I’d still add this anyway.
Obviously, the original edition of a comic is worth more than a reprint.
Long-running series have loyal fanbases, so that even if the story in a particular issue is a little weak, they’ll still sell. Collectors of a series will buy new issues and fill the gaps in their collection regardless. Older issues of Superman, Spider-man, and Batman, for example, will probably always be sought after, if only because they’re Superman, Spider-man, and Batman.
Comic book grading is important. Everyone wants the comics in their collection to be in mint condition. A comic that is discolored and stained, that has a detached cover and is altogether battered and bruised isn’t that appealing.
Great stories sell comics and make them valuable. This is so obvious I feel a little silly saying it. Notable stories can be about a character’s origins, or just general major events. Marvel Future Fight is my favorite.
Writers and Artists
Just as some people collect a specific series, some people collect the works of their favorite writers. This is also related to storylines, as great writers write great stories. If the artwork was done by a famous artist, that can also affect the comic book’s price.
The characters that appear in an issue affect its value, particularly first appearances and guest apperances.
The Overstreet Price Guide is a great tool to work out your comic book values. It has a comprehensive list of comics, giving guide prices depending on their condition. It also lists things that affect a comics value, like the things I’ve listed above. There are also great articles, such as expert’s opinions on comic collecting, and pictures.