IIRC, it's 5000gold max per transfer.

But you can't change factions. If you transfer as alliance, you stay as alliance. So there is no way to transfer gold over to other faction unless by AH. Me thinks..

Bugger then say la. You gave an unclear explanation..

Since FM is a pvp server, you can't have a Horde and an Alliance char on the same account. What you can do is:
1) Buy a new account and start Horde
2) Delete your Alliance char and start Horde

Either way you still need to use the AH as a medium to transfer your gold because there is no other way to trade between inter-faction.