Let me put it another way. Let's say I sell my World of Warcraft account to another player. It violates Blizzard's TOS, but it's not illegal. I may have also obtained the characters on that account through illicit means - using bots. Again, that's not illegal (maybe a DMCA case could be made for it - I'm not familiar - but it's not fraud). Substitute WoW characters obtained through hacks for virtual currency obtained through hacks, and here we are.
Though if selling imaginary world things for real world cash isn't fraud, I have a great vacation home in middle earth to offer you!
This is entirely how many games make their money. Is League of Legends fraud?