Is my iPhone 5C / AT&T Next math wrong here? Thinking about using it...

Hear me out... I think I made a way to make the math work

I am at the end of my 4S contract. I like the 5C but I am looking forward to what Apple may do next year with the iPhone 6 (or whatever they call it).

AT&T is offering iPhone 5C for $27 per month under its Next plan.

Let's say I get the iPhone 5C for that. Over 12 months, I pay $324 + tax for my iPhone 5C, which would have cost $199 + tax if I got a two year contract. So over the first twelve months, I pay $125 extra.

At that point in September 2014, I purchase the new iPhone 6 on a two year contract at $299, switching out of the Next program after turning in my iPhone 5C. I called AT&T to confirm I could do this with no penalty under Next.

What I am essentially doing in that case is paying a $125 early termination fee over the 12 month period, which is less than the $375 normal early termination fee for AT&T. That's savings of $250. I could attempt to sell my iPhone 5C to finance payment of the early termination fee, but that takes work, eBay fees, depreciation cost on the phone, etc. Plus, I would have to pay retail for the iPhone 6, which would likely be $749 for a 32 G model.

So under Next, I pay $324 + $299 + $36 (upgrade fee in 2014) = $659 for two phones: iPhone 5C and iPhone 6.

Under two years contracts, I pay $199 + $375 (Early Termination Fee) + $749 - $300 (value of sold iPhone 5C) = $1,023 for two phones: iPhone 5C and iPhone 6

Am I wrong here? Of course my AT&T service bill never changes during because I can't get a lower bill for being off contract, but that's a separate issue