Anyone who thought the Refco (NYSE:RFX) scandal might soil the market debut of CBOT Holdings (NYSE:BOT), owner of the Chicago Board of Trade, was sadly mistaken.

The IPO was, as they say, hot. The operator of the No. 2 futures and commodities market was originally priced at $45 to $49 a share. The 6% of the company that was sold in the IPO finally went for $54 a share. Talk about buying interest!

The stock opened for trading on Wednesday at $80.75, up 45.9% from the IPO price, but it closed at $80.30 a share. That flat close sounds like the stock was winded, right? Wrong! The stock hit a new trading high yesterday and was up 13.2% for the day. Today? You guessed it -- up about 20% at its mid-afternoon high of $108.50 a share.

Is this the next Google (NASDAQ:GOOG), headed for higher and higher highs?

Well, if you look at the No. 1 competitor and the top dog in this marketplace, you start to understand the excitement. The Chicago Mercantile Exchange (NYSE:CME) IPO'ed in Dec. 2002 for $43 a share and has reached a new all-time high today of $348.50 -- an eight-bagger in less than three years.

So let's take a look at what we're dealing with. Net income for the first six months of this year was $39 million -- up only 20% from the comparable period last year. There are 52.3 million total class A shares. Annualize that gain and it adds up to $1.49 a share, so the stock is trading at 72.8 times my contrived 2005 earnings. That looks really high, especially for a company showing 20% earnings growth.

I know the market liked the CME IPO, and the business model certainly has its charm. But why would expensive analysts, paid by the company to determine what the company is worth, miss the market value (as measured today) by so much when the Chicago Merc, Nasdaq (NASDAQ:NDAQ) , and Archipelago (NYSE:AX) are available for comparison pricing? Some might argue that underpricing is common in IPOs, but I contend that there's also substantial research suggesting that most IPOs are accurately priced.

Here is this observer's simple answer: Momentum is pushing this stock up, but gravity will take hold and bring the price back closer to the Earth-bound reality of its IPO price.

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Fool contributor W.D. Crotty does not own shares in any of the companies mentioned. Click here to see The Motley Fool's disclosure policy.