the fee is collected by 2 parties, one is collected by the agent, say, if you are paying by visa, then part of the fee is collected by by visa, can be up to 2 to 3 %. another one is collected due to exchange rate different, say, sell hk buy us may be 7.85 HKD to 1 USD and sell HK buy US may be 1 US to 7.75...