Is it about the money though? He's reportedly signed for Β£70k a week at Barca! That's a decent raise but it's not a game changer when you're watching your colleague move to United on double his old wage.
If it's about the money, it's probably about Darren Dein's commission more than Song's wages.
I think Dein got in his ear and fucked things up. If they really have tried six times to renegotiate his contract early it's no wonder he came to be regarded as a troublemaker.
In short, I blame Darren Dein.