Now, I know there is most likely people who have already discovered this method, and there are probably already posts detailing how to do this, but to be honest I cbf searching the forums to see if there are any, so don't flame me about trying to claim the discovery. This is how I did it:
1) go to your local AH on the account that you wish transfer gold from
2) look at all the listings of battle pets (I chose a crimson whelping as my gold vessel, as it is typically a sought after pet, and usually sells quickly)
3) buy the pet (I bought my whelping for around 7k), and put it into your pet journal
4) go on your other account (the one that is on the other realm that you wish to transfer the fund to) and use the "put in cage" option on your new pet (in my case, the whelpling)
5) you should now be able to sell the whelping on your new account ( I sold my whelpling the next day on the AH for 9k, a tasty profit if I do say so myself.
Now as you all know, prices vary from realm to realm, so you should make sure that you are investing in a pet that has a stable value on both realms, whelplings are my weapon of choice. However, these baby dragons typically cost upwards of 5k (depending on street prices) so you may have to invest in other pets (or multiple pets) for your transfer to be successful. Any further questions, just ask.
Thank you for your time, and have a good day :)