Why is Action Comics #1 so valuable?

A combination of several factors

• the first appearance of Superman—certainly a cultural milestone
• It introduced the most important superhero in modern history, Superman. It began what's known as the Golden Age of comics. It's probably the most important single comic title of all time.
• Superman is on the cover
• most of the copies have not survived into present day. In WWII it was common for comics to be donated to paper drives to make supplies for soldiers—so many of those 1940s comics are more rare than comics from other eras
• the fact that Superman is still a popular character
• the fact that many people like—and collect—comics

In short it all adds up to supply vs demand. Low supply, high demand results in high prices. And this adds to the cycle—high prices make it more in demand as an investment for future profits.

Amazing Fantasy #15 is among the most sought after comic books of all time

The first appearance of Marvel’s Spider-Man in a comic book is a huge deal among fans and collectors.

Top 5 Most Valuable Comic Books from the Modern Age (1992-Date)

1) Amazing Spider-Man #667 Gabriele Dell'Otto Variant

2) Walking Dead #1, CGC 9.9

3) Edge of Spider-Verse #2: Gwen Stacy Becomes Spider-Woman. Retailer Incentive Edition

4) Spider-Man Collectible Classics #1: So-Called 'Chromium' Edition of Amazing Spider-Man #300

5) Spawn #1 CGC 9.9

Top 5 Most Expensive Comic Book List: Copper Age (1981-1991)

1. Teenage Mutant Ninja Turtles #1 First Printing, Origin and First Appearance of the Team

2. Marvel Super Heroes Secret Wars #8

3. Albedo #2, 1st Usagi Yojimbo

4. Wolverine #1 1988

5. Wolverine Ltd Series #1 (1982): Classic Cover, 1st Solo Book

Top 5 Most Valuable Comic Books of the Bronze Age (1970-1980)

1) Incredible Hulk #181, 1st Wolverine

2) Marvel Spotlight #5, 1st Ghost Rider

3) Green Lantern #76

4) Werewolf by Night #32, 1st Moon Knight

5) Star Wars #1 35c Price Variant

Top 5 Most Valuable Silver Age Comics

Amazing Fantasy #15 (August 1962)

X-Men #1 (September 1963)

Incredible Hulk #1 (May 1962)

Tales of Suspense #39 (March 1963)

Fantastic Four #1 (November 1961)