Yesterday, I clambered back up on my soapbox (yes, again) to declaim against Rupert Murdoch's snipping the price tag on Dow Jones' (NYSE:DJ) (soon to be News Corp.'s (NYSE:NWS)) Wall Street Journal Internet site. Perusing the column, my editor mused, "As a paying customer of the WSJ, the first thing I'll do when they go free online is cancel my print subscription. [Assuming I'm not alone,] the question is this: What percentage of the print revenues is likely to fall away if the online version goes free?"

Guess who got tasked with figuring that out ...

Yes, me. Unfortunately, the plain and simple answer is that I don't know the answer. I've just finished combing through Dow Jones's most recent 10-K, and maybe my eyes are going, but I'll be darned if I could find a line entry stating plainly: "This is how much we make on print Journal subscriptions."

But I can guess. According to its 10-K, Dow Jones averaged a print Journal circulation of 1,733,000 in 2006. 6.7% of those were sold at newsstands at the full, \$1.50-a-pop price. The rest moved at various discounted prices. So what kind of money are we talking about here?

• 0.067 x 1,733,000 x \$1.50 x about 300 (business days in a year) = \$52 million
• 0.933 x 1,733,000 x \$149 (the cheapest annual price yours Fool-y has received in the mail) = \$241 million.

Add 'em up, and my best guess is that Murdoch's move to a free WSJ.com site potentially puts about \$300 million in subscription revenue at risk. If, say, one skinflint in three decides to stop paying for print versions of articles that become free on line, then Murdoch is going to have to make up \$200 million (\$100 million in the above lost print sales plus \$100 million in lost online subscriptions) just to break even on this harebrained idea.

New math
Now admittedly, Murdoch aims to take a page from the playbooks of Google (NASDAQ:GOOG), ValueClick (NASDAQ:VCLK), and Time Warner's (NYSE:TWX) AOL, and make up the difference in increased ad sales. The stated idea is to increase online viewership up to 15-fold by making WSJ.com free. Also admittedly, Murdoch's in good company going this route. In addition to the advertising-loving firms named above, two peer newspapers, the New York Times (NYSE:NYT) and Pearson's (NYSE:PSO) The Financial Times, have likewise adopted free online access business models.

But still, \$200 million? That's a heckuvalot of ad clicks.

Follow along as we parse the logic of this business model-shattering news in:

Time Warner is a Motley Fool Stock Advisor recommendation. New York Times is a former Income Investor pick.

Fool contributor Rich Smith does not own shares of any company named above. Get your free refresher course in The Motley Fool's disclosure policy right here.