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Dotcom stock offerings have lately displayed frenzied pricing not seen since the 2000 tech bubble. LinkedIn (LNKD), which debuted a month ago as the priciest stock in America, has lost one-third of its value since trading began, while Pandora (P), the internet radio firm, has gotten one-quarter cheaper in its first week of trading. Groupon might nonetheless debut with a stock market value that exceeds those of companies like Kellogg (K), Yahoo (YHOO) and Charles Schwab (SCH) .

The market, of course, might know more than me about the future value of these companies. On the other hand, frantic bidding can produce strange results -- like the equivalent of paying $1.15 for a $1 bill. In a sample of online auctions for gift certificates, 41% of winning bidders paid more than face value, according to a study slated for publication in the academic journal Economics Letters.

The gift certificates were from Amazon.com (AMZN) and ranged in value from $5 to $573.45 with a median value of $25. The 506 auctions occurred on eBay (ebay) in September and October 2008. Among the winning bidders who paid more than face value, one in three paid at least 5% too much and one in four paid 10% too much.

Let me dispense with some would-be comforting theories before reaching the inevitable conclusion that we're all a half-step removed from shaved chimps and so can't figure out how much to pay for $25 gift certificates, let alone shares of social networking websites.

The winning bidders weren't paying up to avoid shipping charges on Amazon, because Amazon doesn't charge for shipping gift certificates. Bidders with excellent ratings based on past transactions were almost as likely to overpay as those with limited histories, suggesting the buyers weren't just scammers. Geography had little bearing either: In a follow-up study, author Matthew Jones, an economics PhD candidate at Ohio State University, tested a 2010 sample of similar auctions and found rampant overpayment no matter where buyers were located.

So what happened? Perhaps the biggest clue is that auctions that attracted six or more bids were about four times as likely to end in overpayment as those that attracted fewer than six bids. That suggests the work of something economists call bidder's fever. It's not the most elegant model of behavior; in auctions, especially competitive ones, some of us just go bonkers with the numbers.

Economists have known about the tendency for decades. Some business school professors even run dollar-bill auctions to demonstrate it in class. But Jones' study is the clearest evidence yet of the phenomenon in practice. The upper limit of a gift certificate's value is fairly certain, and someone who's smart enough to bid on one at eBay is smart enough to buy one at Amazon.com.

Jones isn't giving up on rational explanations. "If someone takes pleasure in winning a competitive auction, and if they pay a premium that's equal to the value of that pleasure, then it's possible that they're not overpaying at all," he says. As if his study wasn't depressing enough, now I have to picture people with so little to cheer for that they bid $28 for $25 gift certificates just to celebrate with what I'll assume are zero human companions and more than one cat.

If there are two lessons to be drawn from this, the first is to be extremely cautious about the assumption that the financial markets always gets prices right.

In the long run they're pretty reliable, but in the short term prices can be skewed by over-excited bidders who imagine that they must get in on such-and-such online at any cost before it's too late. A firm called Zynga, now preparing an initial stock offering, might be worth $15 billion, one analyst recently predicted. Among its products is a virtual farming game where players pretend to plant and harvest crops. You know what sells for just a little more than Zynga's theoretical value and also has a hand in farming? Archer Daniels Midland (ADM) . It processes enough wheat to make 70 million loaves of bread a day -- and its wheat business is tiny compared with its corn and oilseed business.

Second, consider listing on Ebay anything in your home that doesn't have a pulse and that you wouldn't miss if it were stolen. Sure, eBay's fees make pawn brokers blush, but don't think of it as an online auctioneer. Think of it as a hangout for buyers with bad judgment.

Follow Jack on Twitter: @jackhough