Much has been made of the Wall Street Journal‘s report that China Mobile will soon start selling Apple’s iPhone, and for good reason: China Mobile is the largest carrier in the world’s largest mobile market, claiming an astounding 759 million subscribers. China Mobile will reportedly offer substantial subsidies for users willing to sign two-year contracts, which will make the phone much more affordable for many users, and the phone could launch just as China Mobile’s 4G network comes online.

But the 180 million consumers who use China Mobile’s 3G network are the the real key to this deal. Apple will have to produce a new version of its iPhone for China Mobile’s TD-SCDMA network, as my colleague Kevin Tofel explains here, but doing so would instantly give it access those 3G users — a group that outnumbers Verizon Wireless and Sprint combined. As All Things D explained a few months ago, if only 3 percent of those 3G users buy the iPhone in December that would translate to roughly 5 million units sold. And those sales could ramp up in a big way as the carrier converts more 2G users to move to the newer network.