Those comic books in your basement could be gold

$2.1 million comic book
$2.1 million comic book

If you have a collection of old comic books in your basement, it might be time to dig them out.

Several recent big-ticket sales bolster the belief among several analysts that collectible comics are becoming a viable alternative investment for some people. (Warning: if your mother threw away your collection, stop reading.)

One example: In 2011 actor Nicolas Cage sold the most expensive comic book ever, one of the 50 copies of the 1938 "Action Comics" No. 1, Superman's debut. The price: $2.16 million, for a copy was once sold for only 10 cents.

Another copy, which is considered to be in better condition, is up for auction on eBay. and is expected to break the record for the most expensive comic book ever sold.

In May, the first Wolverine comic art, "The Incredible Hulk" No. 180 sold for $657,250 at an auction. In 2012, an original Spider-Man piece "Amazing Spider-Man" No. 328 by artist Todd McFarlane sold for $657,250.

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And eBay says it has had $4 million in comic book sales so far this year, 14 percent more than last year.

How to invest in comic books
How to invest in comic books

"The collectors of comic art have become much more like investors in many ways. They can get their money back on this kind of stuff. Trying to buy it now is a lot more expensive than a few years ago, so there's definitely growth," said Augie De Blieck Jr., a columnist for Comic Book Resources.

"You can get some average pages for a $100-$200, but a lot of the more key pages these days are going for higher numbers," said De Blieck, who has been buying comic art for 15 years.

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The market for rare comics is growing partially thanks to Hollywood, said Vincent Zurzolo, COO of Metropolis Collectibles and a 27-year veteran of the business.

"I think the advent of the movies, I think the increased visibility of comic book prices, the realized prices at marketplace, have really helped to galvanize customers, bidders, people looking for alternative investments to find comic books," said Zurzolo, who is getting ready to sell early issues of Batman owned by creator Bob Kane.

The economic recession in 2008 is another factor, Zurzolo said.

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"After the stock market was extremely volatile, the real estate market was extremely volatile. So people were looking for tangible assets to put their money into. And what did they see? They saw all these superhero movies coming out. And they said 'wow, maybe I can invest in the stuff I loved from when I was a kid,'" said Zurzolo, who owns, which sold Cage's record-breaking comic book.

Experts warn that not all comics are good investments, so how can you tell if yours is collectible? The key is rare issues, preferably that feature the debut of celebrated characters or key plot twists, said Zurzulo.

And the older, the better. The 1930s and '40s are the golden age of comics, and those are some of the most-prized titles.

So if you're looking to buy comics as an investment, you should "collect what you like, figure out what your budget is and talk to an expert," Zurzolo said.

"But a lot of this is about the nostalgia of the collectible ... a lot of it is the story behind the story. It's not just the story in the comic book. It's the story of how that comic book touched their lives," he said.

—By CNBC's Silvana Ordoñez and Morgan Brennan