Real money transaction.

PoE has a pretty free market since 99.9% of all items are tradeable to other players, that's a huge part of the fun for me, selling items I find, or finding a niche in the market.

Naturally, with no trade restrictions, you can give a very expensive item to someone and they pay you with real money somehow.

I don't think he RMT'd, but the account he's playing on clearly plays the game a lot, and built up his character so that even a monkey could sit down and play.