I get that it's more valuable than Superman #200, but why 9 million dollars valuable. There's a poorer quality one at 5 million, but that also means that there's other copies in existence.
It's also not the first Superman comic, what about Action Comics #1?
Why is the Call of Cthulhu (Weird Tales, Feb 1928) about $50k?
Or in terms of characters, what makes Superman worth 3x more than MARVEL #1 or Batman?
Superman was arguably the first super-hero, and certainly the first successful/popular one. And Superman #1 is the first time a super-hero got their own dedicated comic book. It has long been generally considered the third-most desirable comic book issue in existence, after Action Comics #1 (first appearance of Superman) and Detective Comics #27 (first appearance of Batman).
This copy of Superman #1 was graded as a 9.0, which basically means it's like-new, despite being 86 years old. And it's naturally in that condition without ever undergoing restoration, which affects the value. Of all known unrestored copies of Superman #1, this copy is in the best condition.
That said, there are at least three known comic book copies that would be valued more highly: two known unrestored 9.0 copies of Action Comics #1, and one known unrestored 9.2 copy of Detective Comics #27. If any of those were to be sold at auction today, their value would almost certainly be a lot higher than $9 million, in part due to this Superman #1 auction setting a recent precedent.
It's also not the first Superman comic, what about Action Comics #1?
Why is the Call of Cthulhu (Weird Tales, Feb 1928) about $50k?
Or in terms of characters, what makes Superman worth 3x more than MARVEL #1 or Batman?