Sure, there are key issues that can cost you four figures or more. Then there are KEYS - the ones that bring in the serious money; we're talking millions of dollars. Welcome to the big leagues of comic collecting.

Did you know that a graded 9.2 Fantastic Four #1 averages over $500,000? It's true. And why wouldn't it? This is the comic that launched the Marvel Age. But that's nothing to the 8.5 Action Comics #1 that exchanged hands earlier this year. That comic brought over $2 million.

Want me to really make you want to vomit? That multi-million dollar price tag is a bargain if you compare it with the 9.0 AC #1 that made the Guinness Book of World Records when it sold for $3,207,852 in 2014. In the financial department, Superman is your champion. By my best count (and Google search), his first appearance has sold for $1 million or more four times. I'd wager that a near-mint Action Comics #1 will surpass the $4 million point within the next two or three years.

If you're like me, you read statistics like that and you start wondering about the other comics that are that valuable. Wonder no more, for I have done the research for you. You are welcome.

DETECTIVE COMICS #27

Holy hand grenade, Batman! (Two nerd references, one sentence. Top that.) In 2010, before Superman had to go and one up the Caped Crusader, Batman's first appearance held the record for the most expensive comic ever sold. That year, an 8.0 DC #27 (Did you know that's where DC Comics gets the DC? Literally the company is Detective Comics Comics.) brought an astounding $1,075,000! Yes, that sentence is worthy of an exclamation point.

AMAZING FANTASY #15

Being a younger comic than the debuts of Superman and Batman, it makes sense that there have been more Amazing Fantasy #15s sold than the latter two. Still, the first appearance of Spider-Man brings some...amazing (you knew it was coming) prices. The record for an AF #15 (and, yes, I giggle like a 13 year old every time I type AF) was $1,100,000 for a 9.6 in 2011.  Five years later, a 9.4 Spider-Man first appearance fetched $454,100.

BATMAN #1

Once again, those old Batman issues have the potential to make someone very rich. In 2013, a 9.2 Batman #1 sold on Heritage Auctions for $567,625. This is a huge comic, the influence of which can still be felt today after the fallout from the Bat-wedding. Not only was this the first comic in the first self-titled Batman series, but this issue featured the debuts of two iconic characters: the Joker and Catwoman. I can't help but wonder how much that 9.2 would sell for in today's market.

X-MEN #1

Another score for Heritage Auctions, a copy of the first appearance of the X-Men sold for $1,200,000 in July 2012. Why would that comic break the one million mark? Yes, it's a monumental issue, and it's the first appearance of one of Marvel's most popular properties, but this is more than that Batman #1. The deal here is that this particular X-Men #1 was graded by CGC as a 9.8. That's jaw dropping. Not only is it a mega-key issue, but that grade makes it extremely rare.