Still not a deal, because Apple will pretty much always give you at least 50% of last year's device in trade-in value toward the new one, especially the Pro series.
For example, I'm trading in my 15 Pro Max for $650 (that I originally paid $550 for after trading in my 14 Pro Max last year) and financing the 16 Pro Max through ACMI for $22.87 and will be activating it on my $25/mo US Mobile plan (taxes and fees included), coming out to a monthly cost of $47.87/mo for the phone AND plan vs $70.55 (plus tax) for the same exact device and comparable plan on Boost, and I can also upgrade every year by just doing this same trade-in process again and again (as I always have).
Boost isn't giving you a free phone. They've inflated the cost of their base plan to trick people into believing they're getting a heavily subsidized iPhone, effectively still charging you for said phone just through the plan instead, and clearly it's working...