Advcash is similar to perfectmoney in the sense that I've never heard of a chargeback case from them. All of their transactions are final, which is why a lot of people are willing to buy Advcash straight up with BTC.
But the 50% markup does seem a bit too good to be true. The guy could easily get +10% or less on spot just by using one of the exchangers listed on Bestchange.
Instinct tells me this is probably a scam, but perhaps not in the sense that he'll charge you back or use a stolen CC. He's more likely trying to do social engineering on Paxful support without actually sending you anything. I wouldn't risk it either way.