You do know that you pay EXTRA every month on a subsidy plan, correct? I mean a man of your intelligence and financial savvy surely should know this. You pay an EXTRA $15-25 per month. On 10gb mobile shared plans and up you pay $25, so $25 x 24 months = $600. Now add $600 to the subsidy price, don't forget to add the $40 activation fee and tell me how that compares to just buying the phone outright.
Edit: Well I thought about it and as I'm sure you would be busy preparing a financial investment package for a multi billion dollar client figured I would just do the math for us. Oh and that monthly credit is funny enough in that same picture you posted.
16gb iPhone 6 in your picture
AT&T subsidy: 199 subsidy price + 25x24 months = 600 + 40 activation fee = $839
Full price = $649