Anyway, while seashells are what drew me to the article initially, we're going to take a detour, because what's really interesting about the article involves pricing.
During the 17th century, a Glory of the Seas Cone sold at auction at triple the price of this masterpiece by Vermeer. Today, that Vermeer would cost easily tens of millions of dollars, while a Glory of the Seas cone goes for about $40 on ebay. Seashells, apparently, were once considered more valuable than even the finest works of art. This seems ridiculous on the scale of Dutch tulipomania, and most likely mania had a lot to do with it. However, as the Smithsonian article posits, it seems there was actually some degree of economic justification for this pricing discrepancy:
But what seems common to us could seem breathtakingly rare to early collectors, and vice versa. Daniel Margocsy, a historian of science at Northwestern University, points out that Dutch artists produced five million or more paintings in the 17th century. Even Vermeers and Rembrandts could get lost in the glut, or lose value as fashions shifted. Beautiful shells from outside Europe, on the other hand, had to be collected or acquired by trade in distant countries, often at considerable risk, then transported long distances home on crowded ships, which had an alarming tendency to sink or go up in flames en route.
Eventually, due to a combination of safer transportation, increased global trade, and, most importantly, the discovery of the native habitat of this particular species of shell, the price of the Glory of the Seas Cone has plunged. By contrast, Vermeers have skyrocketed in value as collectors became more discerning, and many contemporary works were gradually lost or destroyed.
The point I'm trying to make is that what seems scarce may not really be so rare, and what seems commonplace may not be so common, especially after the passing of time. (Anyone who's played MMORPGs for a good length of time has probably seen this phenomenon in fast-forward several times, but that's fodder for another post.) I'm not saying you should go out and load up on baseball cards, (the infamous Billy Ripken F*ck Face error is no Vermeer, I can assure you,) but I wouldn't bet the farm either on somethig whose value is based solely on perceived scarcity and mania-driven demand.