First, make a character you are willing to lose, a DK or a level 1 char. Then put the gold you want to Xfer to another server/ faction on that char and request a Faction/Realm change. If you do this by Credit Card / Ideal etc, you can transfer you're character without having to inmiditely pay real cash for it, but you're char gets transfered.
So, for example, i want to move 5k cash + alot of mats from my Horde char to Alliance, create a Horde DK, put the items + Gold on it, request a Realm/Faction change, wait 10 minutes and you're char is Alliance.
(Be sure you're Credit Card is empty, or you end up paying )