This is nothing new; you're still going to be stuck paying monthly for at least 12 months if you don't trade in pretty much a last gen device or slightly older. The word "free" is unfortunately what gets a lot of average consumers. It may not cost anything then; but yes you either cover the price of the current device being sold with a trade in and some cash; or paying monthly with your expensive data bill. There's a reason I go on Ebay; Amazon; Back Market or Walmart for my tech used; refurbished; or new but independent from carrier contracts. Nobody should really be "in debt" to a company over a mere smartphone. There's always cheaper options without losing what you love about one.
Nothing is free, especially in the USA. This offer shows, for a thousand times, that the data plans costs no more then 10-20$. The rest is covering the phones costs or is just pure profit
It's like buying two phones at the price of one.
Enough, but not enough...