Well, sure - I mean, the carriers aren't offering you "a free phone," "$850 off," or whatever out of the kindness of their heart. Flagship cellphone prices are unpalatable whether we're talking a decade ago or today. So, there's a song and dance or a magic show necessary to get you to buy in. I happen to feel that this method is a bit more transparent then the fabrication of savings that was the "subsidy" of yesteryear.
But, that said, T-Mobile's offers have been legitimate for me.
I've gone though two upgrades with T-Mobile using their trade-in "Up to $XXX off" offers. Once in 2016 for the iPhone 7 and last year for the iPhone 11.
In 2016, my family and I mostly owned iPhone 6 and T-Mobile offered "up to $650" for each of the families iPhone 6 ($450 for my mother's, 5S). After 2 years, yea - the iPhone 7's that we ordered were paid for by the monthly bill credit payments (except for my mother who paid / owed $200 since she traded in a 5S iPhone).
In 2019, we traded the iPhone 7 towards iPhone 11. We were offered "half off" or "up to $350" for our iPhone 7.
Whomever, you get your offer from, yea, it's absolutely still a ploy to keep you locked-in to the carrier. But, compared to the "carrier subsidy" the savings is legitimate this time - not a loan you can never stop paying for even after you repay the principle. Yesteryear's "ETF" for switching carrier or dropping service was just what you owed on the loan you were given when you originally bought your phone.
