$31,500: That’s the approximate value of a “very fine” copy of the 1941 All-Star Comics #8, officially graded at 8.0 on a scale of 0.5 to 10. A 9.2, “near mint” copy would likely be about $90,000. Why so costly? How could printed paper be worth so much?

All-Star Comics #8 features the first appearance of Wonder Woman, comics’ first (and, at the time, only) superheroine, so its status is due at least in part to its important place in the history of comic books. But its rarity—and the rarity of any comic from the same era—is what gives this book in particular such a high value.

It is estimated that only about 10% of the original printings from the 40s still exist today. There are multiple reasons behind the rarity of early comics. First is simply the number of these comics that were available from the time they were created: printings of comics were mostly relatively small, compared to today.

Second is the short-lived nature of the material used to create them: comics were formerly printed on acidic, pulp paper. This type of paper reacts with oxygen, causing it to literally disintegrate over time. Even comics preserved in hard cases can still break down, due to the fragility of the paper.

Third is the way that these early comics were handled: in the 1940s, comics only cost 10 cents, and it wasn’t until the 1980s that they were recognized as having value. Initially, they weren’t treated with any more care than newspapers—kids drew on them, cut them up, ripped out parts to give away to their friends. In fact, in 2013, a man found a preserved original copy Action Comics #1 (the first appearance of Superman in 1938) hiding among newspapers as insulation in his $10,100 fixer-upper home. Amidst the excitement, he and his family members ripped the back cover, bringing the grade to a 1.5—even so, the comic fetched over $100,000 on an online auction site.

Because of the small printings, the fragile material, and the way early comic owners handled their books, it is very rare to find any original copy of All-Star Comics #8—the possibility of finding one without damage is nearly nonexistent. To be considered a 9.2, the book must be close to perfect. An 8.0, a “very fine,” is likely the most pristine copy that anyone will find: even this lower grade means almost no wear and tear.

The grading and establishing of the monetary value of comic books is done in a very specific way by the Certified Guarantee Company (CGC Comics). When someone finds a comic book that they want to have graded, they must mail it in to CGC (or wait until a comic convention to have the grading done in person, especially if the comic is particularly old and rare). CGC gives the comic a grade and returns it to the owner in a hard plastic case, with a sticker across the top stating the grade and the reasons for the grade. It must then be kept in the case to maintain the grade: if the case is opened, the grading process must be done over again for the grade to remain official. Opening the case or reading the comic therefore has the potential to significantly decrease the value. The grading system creates an odd paradox for comic lovers: once you become the owner of a valuable comic, it ceases to be an interactive book to be read, and instead becomes more of an object, a static piece of artwork.