Selling a 1 year old iphone on Craigslist usually gets $450-550. Selling a 2 year old iphone on Craigslist gets about $250-300. The bottom is about $150 on craiglist for an old but working 3G. Gazelle is significantly less than these figures, and there is a risk they can under-evaluate you.
If your phone breaks Apple will usually replace it for about $270. If the phone is older you can then choose to upgrade through Craigslist. Best choice is to have them meet you at your ATT store and verify that it will switch. Also make sure 'Find my iphone' is off, and check all the functions to include wifi. Also look at the water sensors. I prefer Craigslist for this because you can fully inspect before buying. Plan to pay the prices I quoted above, meaning a 2 year old phone on craigslist will cost you as much as a replacement from ATT. HOWEVER. Even your broken phone will sell well. For that put it on Ebay as craigslist is too small of a market.
Where is the water sensor?
When buying on CL or EBay, what is required to be able to add to my Att plan.
It appears that if others on my plan don't upgrade as often and if I sell at the right times, I would prob save some money per month. It also appears that it's kind of a pain to "time" the market, not get ripped off, etc.
Still have no idea if I should do it or not. Wish it wasn't so difficult.