Att offered such good trade in rates for my phone that it’s been effectively free to upgrade to the last two generations.

I hear people say things like this about phones, laptops and cars, but anecdotally I have never once seen any sort of trade-in offer, and only rarely and arguably on any kind of lease or lease-to-buy arrangement, where I would consider that even remotely true.

it's not free because it's priced into the phone plan (phone plan price is jacked up), unless you got grandfathered in w/ a good rate.

Or even Google itself. I got a 150€ trade in rebate for an iPhone 8 with a cracked screen.