Im Ahtalon and i play on Antillia, i have encountered a very cheesy exploit:
my Premise is: Items should only be transferred between cities with storage sheds (so only between befriended cities with a gold-fee).
Heres the deal you can easy surpass that:
you can create a sell order on the auction house, then teleport to any city you want and when you dismiss the order you will get the items in your inventory. That way you only have to pay a very small fee and you can transfer intems between all cities.