AT&T plans to subsidize as much as $200 of the price of the 3G iPhone, according to a Fortune report. Citing a person “familiar with the strategy,” the report states that the subsidy would bring the price of the base-model 3G iPhone to $199 for customers who sign two-year contracts, a price that would help AT&T lure more customers away from rival carriers Verizon, T-Mobile, and Sprint. Subsidized iPhones will reportedly be available…