No matter how you choose to upgrade you'll wind up paying full retail price. Either through device payments or services charges from your carrier, it's always been unavoidable. With the upgrade program if you decide to upgrade every year and turn in your phone, you only end up paying half the retail price for it and half the price of applecare
sorry I don't get this part, how are you paying half the price? because you're turning the old one in? because it sounds like you can do that with any plan http://www.apple.com/iphone/trade-up/