Apple's iPhone has been a big hit for exclusive U.S. carrier AT&T -- but it's an expensive one.
In its annual report to the SEC (PDF), AT&T said selling, general, and administrative (SG&A) expenses increased $1.1 billion in 2007, up 10% year-over-year. About half of the jump -- $572 million -- was "due to increases in sales and advertising expenses and Apple iPhone-related costs." We assume -- but haven't confirmed -- that the number includes AT&T's kickback/revenue share with Apple. That tariff may be as high as $15 per month, per subscriber. We'll update if we get more information.