I can't believe the amount of people that quote a 2-year old, incredibly incorrect story, still.
Next lops off 25 dollars per month from the 40 dollar monthly access fee, so you only pay 15. You own the phone, you don't return it unless you upgrade *before* you pay it off. So saving $25 per month for 2 years amounts to a 600 dollar savings. And you only pay the monthly fee for as long as it takes, so a 750 dollar phone only ever costs you 750 dollars. No more, no less.
With a contract, you pay 200 dollars up front, and then you pay an extra 25 dollars per month forever, but for arguments sake, we'll use the exact same 24 months... So that 600 dollars saved on Next you now pay onto that phone, so your 750 dollar phone costs you 800 after 24 months... So after 24 months, you're already behind 50 bucks from where I am.
But then if we keep the phones, things get interesting... I stop paying my fee, yet you keep paying 25 dollars more per month. If we kept it another year, my 750 dollar phone has only cost me 750 dollars. Yours has now cost you 1100.
Maybe next time, don't plagiarize, check the date on the article... And read the comments where the author has been corrected.