Different MMOs can often have very different rules regarding this sort of thing. In Everquest II, for example, you could buy pretty much anything from another player with cash. You could even buy someone's character! Or sell your own characters. It was all totally legal. I've never seen anything like that in any other MMO, although I do remember Diablo III (which I know is not an MMO, but still...) letting players buy and sell gear for real money. You try anything remotely similar in most games, though, and you will be banned.
With that in mind, I could easily imagine some other MMO entering into partnerships with third-party entities like that. Someone coming here from such an MMO might not be aware that SE doesn't do this.
My initial gut instinct is, yeah, of course that's not legitimate, but I can still imagine someone who does have some common sense falling for a scam like this, due to having a similar experience legitimately in some other game.
I appreciate Dustytome's warning, and think it is quite timely.