Sometimes it's useful to have gold on the opposing side, I play alliance and often note horde prices can be cheaper. Also there are items I'd like to be able to buy and send to my alliance characters. However I don't want to lose gold on the cross faction Auction House!
Solution
As of patch 3.3 the following change has occurred:
As such we can now give gold to our opposing faction characters using:Bind-on-Account Items: Players can now mail Bind-on-Account items to characters on the same account and realm regardless of faction. Please note this only applies to Bind-on-Account items. Other items or gold cannot be sent via mail to characters on the same realm and account if they are from differing factions.
Wintergrasp Commendation
Binds to account
Item Level 1
Use: Grants you 2000 honor.
These cost 30 Stone Keepers shards or 9 Wintergrasp marks of honor a time.
Passing 5 of these = 10 000 honor, which allows you to buy a single epic gem on the opposing faction.
Therefore you can give some initial AH investment money without having anything taken from you.
This may be of help to people in a similar situation to myself where prices vary a great deal both sides of the AH and are fed up of losing gold in ah cuts.