Most comics are worth modest money and a few are worth a great deal, and the difference is almost never the story inside.
What moves the number
Which issue, and whether it carries a first appearance or another event collectors track.
Which printing. A first and a later reprint look similar on a shelf and are not the same object.
Condition, and in this trade that means the spine above all, then the cover gloss, the corners and the page colour.
Restoration. Any work done changes what the book is, and it must be declared.
Why two of the same differ
Because one has a tight spine and flat cover and the other has been read flat on a table. How comic condition is described.
How to find out rather than guess
Identify the issue and printing from the indicia, not from the cover art. Then compare completed sales at the same grade, graded or raw, and do not mix the two.
If you cannot grade it, describe it and give a band. "I would call this very fine, but I do not grade" is a sentence that sells.
What a box of comics is worth
Usually more as sorted runs than as a box. An hour spent sorting by title and era is the most profitable hour in this category.
Questions people ask
Is pressing worth doing?
Opinion is divided, and either way it must be declared. Do not treat it as free value.
Does a key issue in poor condition still sell?
Yes, often well. Reading copies of sought-after issues have a real market.
What about Indian editions and reprints?
A real market of their own. Describe the edition precisely rather than comparing to the American original.
More: pricing comics, packing comics.