Even in a comic collecting subculture which has developed an unimaginably complex set of rules about how it attempts to assign value, the original art market is considered mysterious. Top-end pieces often trade hands in private transactions for undisclosed amounts. The existence and provenance of major pieces is often relegated to friend-of-a-friend rumor, and just when you're tempted to think 99% of what you hear is bullshit, something like the complete set of Ditko Spider-Man pages from Amazing Fantasy #15 surfaces, and everything you thought you knew changes.
In contrast to this atmosphere, many of the major pieces from Batman architect Jerry Robinson's world-class comic art collection have been well-known to the original art community, and he has loaned them out frequently for museum exhibits in recent years. Among the most famous of these is the cover of Superman #14 by Fred Ray, and the cover of Detective Comics #69 by Robinson himself.
The cover to Superman #14 from 1942 is one of the most iconic images from the character's formative years, and is perhaps just a small cut below the covers of Action Comics #1 and Superman #1 (and the original art of neither of those is known to survive) in terms of imprinting the image of the Superman mythos on the consciousness of the public during his early years — particularly when it comes to developing the Truth, Justice, and the American Way aspect of the character.
What's this piece going to go for? Informed estimates are all over the map, but it's been an interesting year in both high-end comic and comic art values. Three comic books have gone for over a million dollars each this year (2 copies of Action #1, and a Detective Comics #27), and the Frazetta cover of Weird Science-Fantasy #29 traded hands for $380,000 in June in what is widely considered to be the record for a comic book cover (but again, with the secrecy in the hobby, you can never by 100% sure).
That's an excellent question which comicconnect.com hopes to answer in an auction starting November 10, where both the Supes #14 and the Detective #69 cover pieces are going on the block.