If you bought your iPhone 4 in June of 2010, then your ETF to leave AT&T is $175. If you add that to $199 (for the 16gb model) to buy the iPhone 4s on Verizon or Sprint your total is $374. Yet, if you wanted to upgrade right now on AT&T prior to eligibility it would cost $449 for the 16gb model. So basically it costs significantly less to switch than to stay with AT&T assuming you were an early iPhone 4 adopter. The math gets closer if you bought the iPhone 4 more recently (and thus your ETF is higher), but still in most cases it will be cheaper to switch. Am I doing the math wrong here, or what else am I missing? Or is AT&T just stupid if they don't bump up people's eligibility?