I had a promo because I wasn't on an unlimited plan on any of my lines (was on some old legacy retention deal) and got three 12 minis for "free" by trading in an 11, 6s and 7. Had to pay $20 upgrade fee on each plus the taxes but no monthly payments as the credit was $700 for each phone. I will of course be paying more for my plan now, but I'm also saving money in some other ways (on the monthly disney+ subscription for example since it's included with the unlimited plans, and 6 months of apple music for all three of us, which saves about 90 bucks as we were on an Apple family plan which is $15/month - will go back to that when this expires). Figured at the end of the day I am paying about $30 more per month now, which is roughly the cost of one new iphone. So I figure I got two phones truly for free. We also now have Hulu which is something we had thought about getting anyway.
So Verizon gets more out of me per month for the next two years (and I am sure they're hoping that continues long after), and I can't leave (which I wasn't planning on doing anyway), plus the activation fees. That's I guess what's in it for them. It was also an opportunity for them to try and sell me a whole bunch of other stuff I didn't need like accessories and protection plan (which I declined). They may get good deals on the phones themselves, and they'll get a little something for the old phones. But at the end of the next two years I can make some changes and try and see if I can reduce my bill a bit again.