You can get a secondhand iPhone 7 for much less, and I’d (genuinely) wonder if the newness, missing features (or difference in their quality) are really worth the extra $850?
Having just upgraded from a 6s to an 11, I’d say… meh? The 11 is nice, I guess, but apart from having a new battery and being slightly more responsive (and on the downside, no fingerprint scanner and no headphone jack) it’s functionally pretty equivalent.
I've never owned an iPhone, but this is basically the framework I operate within when thinking about most purchases, but especially phones. If the question of what it offers me is tenuous at best, I don't have enough extra money to burn that I'm going to spend anything close to that on upgrading, and usually never upgrade, instead just replacing one that was either stolen or broken in a horizontal purchase within a budget of around $500