I had no idea you can trade it in at the Apple Store.
I always thought you had to ship it.
on a side note, is my 4 year old iPhone 11 even worth trading? I say its in great condition
I also have an iPhone 11 (Pro Max 256GB) in pristine condition, no scratches on phone or glass cracked and looks like it's right out of the box. I looked at trade in prices and expected a lowball offer. Apple will give me $300 for it, but with my carrier, ATT wireless, they are giving me $830 (value applied to my monthly bill) over 36 mos.
I would hold out one more year, since functionality hasn't changed much from the 11 > 15 in my use-case scenarios, but I would get a boost in battery length +6hrs and new battery since it is a 4yr old phone now and most likely hovering at around 60% or less maximum battery capacity which benefits me the most out of any new features of the last three generations.
Since I won't be changing carriers I will probably go through ATT. Was expecting at most around $400-$450ish from any place including ebay or reselling it myself, but at $830 value (only a -$330 value at 4yrs) it's hard to pass up, even when you are trading in with a much older phone.
IMHO, keep it as a spare mobile pocket computer for movies, youtube, web browsing etc. if you can't get more than $300 for it which I would have if it weren't for the $830 trade-in value and I've kept all my iPhones from 4, 5, 6, 7, and now 11 will be the first time I give up/trade in.