Like most other hobbies which include the collecting of this or that class of items, value often becomes a subject of discussion when dealing with comic books. Prices for things like first appearances of certain characters or pivotal events often drive up the prices of issues. The passage of time is another factor when determining worth. But, what is worth? Worth is completely relative.
Let's look back at the early 90s when the comic book collecting bubble effectively burst. Everyone knew that Superman was dying. Thus, they all fanned out in hopes of getting one, if not a bunch of issues. Many people who did so, didn't even previously collect comics or even have any real interest in the medium itself. They were merely speculating on the future value that might it might bring.