If you are looking to sell comics, be aware that condition dictates much of how much a comic is worth. chipping of the spine, those little creases along the stapled edge, drops the value of a comic significantly. Grading, or "slabbing" a comic can increase its value tenfold, as someone independently has said this is the condition of the comic on a 0 to 10 scale. Note that grading does not automatically set a price for a comic. That is determined by how much collectors are willing to pay for it.
these days, collectors primarily look for what are called "key issues", books containing the first appearance of a character or a major event in the character storyline, usually a death such as that of Robin or Gwen Stacy. The first appearance of Deadpool, in issue #98 of The New Mutants, sells for anywhere from $200 (ungraded) to $900 (graded and signed).