On Oct 19th, AT&T or Verizon will also give you $700 credit ($29.17/month) when you buy two iPhones. Maybe you have to switch carrier to get the credit, i.e., Verizon <-> AT&T.
You have to pay $749 x 2 phones + Tax(Sales tax rate of $1498) - $700. For example, sale tax rate of my county is 6%. So, total payment would be $887.88 for me for two phones.
Since I can sell them for $300 each after two years later, total amount I would spend is $288 for two years for two iPhones, or $144 per phone for two years including Tax.