If you are like me, you have 2 accounts with 2 factions on the same server. Ocassionally one of my characters is starved for gold, but paying the 15% goblin AH fee and not being able to transfer all your gold because of hefty deposits make it extremely hard and frustrating. When I wanted to buy my paladin an epic flyer, it would not only cost me 5200gold for the damned thing, but id also need to pay another 1000g in taxes! I found a solution that I have been using until this day, saving me thousands of gold.
The First problem- 15% AH cut is brutal, but you can avoid this completely. Depending on the amount of gold you need, you can buy an item and sell it for 1copper(duh). However, the higher the amount of gold you need, the more easily you can swamp the factions market generally lowering the price of the item making doing this method essentially useless (and sometimes it makes it worse!). When dealing with large numbers, its very important to deal with an extremely popular commodity; ore, gems, netherweave, enchanting mats, rep items, etc.
Dealing with these commoditys may take a couple days to sell (try not to sell too much at one time to avoid swamping), but for 2-5minutes/every 2 days work, it can potentially save you thousands (yay me!).
The second problem- Deposit Fees are annoying when you're strapped for cash and you want to transfer as much as possible. However, the trick I use to avoid this is to deal in commodities with EXTREMELY low deposits. The 2 best by far are rep items (aldor/scryer etc.) and enchanting mats. Both easy to sell in large numbers, both with miniscule deposit fees. If you cant get enough of these items, gems are another good option.
If you can avoid it, try not to use ore/leather and ESPECIALLY not netherweave.
I hope you enjoyed my short guide, and I hope it helps you as much as it helped me!