Analysts scratching their heads about how they could have so badly underestimated Apple’s (AAPL) iPhones sales — and as a result, its revenue and earnings — in the quarter that ended March 27 need look no further than the Chinese market for iPhones.

The 8.752 million iPhones Apple sold in Q2 2010 beat Wall Street’s estimates by 25% to 30% — or nearly 2 million phones.

Where did those sales come from? A big chunk of them, it seems, came from China. Listen to this exchange between Barclay’s Ben Reitzes and Apple COO Tim Cook during Tuesday’s earnings call with analysts:

Reitzes:
Did China meet your expectations?
Cook:
China has been interesting. If you look at greater China which we define as mainland China, Hong Kong and Taiwan, the iPhone units were up year-over-year over 9 times. We added another 800 points of distribution in China. The revenue, we have never released this number before but I will do this in this particular case, through the first half of the fiscal year that we just completed for the six month period our revenue from greater China was almost $1.3 billion and this is up over 200% year-over-year. So we are well pleased with how the company is positioned to take advantage of the growth in greater China. (Transcript: Seeking Alpha)

Going to the back of our envelope (which is where we usually get in trouble), if you divide $1.3 billion by the average selling price of the iPhone in the March quarter ($622), you get nearly 2.1 million iPhones. That could be off a bit, but you get the picture.

[UPDATE: I got into trouble. Apple has confirmed, as several readers suggested, that Cook’s $1.3 billion was referring to all Apple sales, not just iPhones, which ruins my unit sales calculation. It has not offered an estimate of what percentage of that revenue came from iPhone sales, but at least one China watcher (iPhonAsia’s Dan Butterfield) suggests that it would be well over half.]

Most of the iPhone-in-China stories we’ve read suggest that the launch has been a disaster for Apple. (Two notable exceptions: Dan Butterfield’s excellent on-the-scene reporting in iPhonAsia and a research note last January by Morgan Stanley’s Katy Huberty.)

A million or so Two million phones in a country of half a billion cellphone owners may not sound like a lot, but according to Huberty, the addressable iPhone market in China (which she defines as people with with an annual income over $20,000 and an average cellphone bill of $22 per month) is about 50 million. If she’s right, Apple may have captured 4% a significant percentage  of it in the space of six months.

See also:

• Coming soon: 4-5 million Chinese iPhones
• China iPhone launch a ‘disappointment’
• Inside Beijing’s iPhone black market

[Follow Philip Elmer-DeWitt on Twitter @philiped]