The one time we used Swappa we got a piece of crap phone. But it was an Alcatel Idol 4s windows phone for a hundred bucks (my wife just had to have another windows phone :-\ ). She got her money's worth out of it.... but between that and all the third party scammer's on Amazon/eBay/Craigslist/Walmart marketplace etc we only buy new phones on clearance now. I find better deals new than used all the time. I just picked up a brand new factory sealed Google store unlocked pixel 3xl with the full Google warranty for $369. IMO buying used isn't worth it anymore. I'll sell used because I'm honest and am OCD about my phones, including the batteries, and I state exactly the condition they're in in every way, no surprises.
Unfortunately that doesn't seem to be the norm