Ive bought on ebay.sold on ebay. No problems.
Bought a used Xperia Z once on amazon. Worst idea ever. “Like new condition” was not at all close to like new condition. It looked like someone jumped someone for it in a dirt field and it was shipped without being cleaned (loads of fingerprints on the screen) it looked gross.
Was banged up. Phone wasnt even factory reset. Then i find out the esn is bad for someone bailing on their contract with the carrier so i couldnt activate it even if i wanted to without paying the 400 tmo still wanted from the original owner.
I eventually sent it back after the seller denied having any clue about the condition of the phone claiming they were selling it “for a friend” who used their account on amazon.
But i did get a steal on a nexus 10 for 150 (charger case and n10 with a screen protector on it) on ebay
And a used nexus 7 2013 for a whole 79 dollars also with case and screen protector charger etc also on ebay.
I like swappa but ive never pulled the trigger on a deal so far