In 1952, a pack of Topps baseball "picture" cards cost a nickel -- not a bad price for some brand-new "giant size" cards and a stick of gum. But suppose you want the prize card -- a Mickey Mantle rookie -- from Topps' first true baseball card set (in 1951, the cards were more like game pieces). In that case, you're going to need to multiply that nickel about one hundred million times over.

That's because a mint condition 1952 Topps #311 Mickey Mantle was just auctioned off for $5.2 million to entrepreneur and actor Rob Gough.

The card breaks the previous mark set by a 2009 Bowman Chrome Draft Prospects Superfractor Mike Trout card.

As for Honus Wagner's famed T206 tobacco card, which has historically dominated the leaderboard as the most expensive card, one sold this fall for a then-record $3.25 million.

But what makes this Mantle so unique, above all others? Well, there aren't many of this card -- and certainly not in such good condition. This one was graded as PSA 9 -- or mint -- while only three PSA 10 "gem mints" are known in existence.

As for why there are so few, that's actually a fun story sure to give card collectors some indigestion.

Mantle's card was included in the final Topps series that year, and it hit the market so late that interest had already shifted from baseball to football. With surplus packs sitting in the Topps warehouse for years, when Topps needed the space, they simply got rid of them. Since this was long before the baseball card hobby market existed, they didn't donate the cards or sell them. Oh no, they dropped them into the Atlantic Ocean.

So, some octopus out there surely has one killer card set. They do collect things, after all.