The cost of a currency exchange is usually determined in one of two ways. Either the client has a specific currency amount and wants or needs to realise as much as possible in the currency they wish to 'buy', or, a client needs to purchase a specific currency amount and the rate of exchange is what dictates the cost of buying that sum.
When you have a monthly or ongoing currency exchange requirement, it is wise to reflect on which of the two scenarios matches your need to exchange currency.
Our client charges us with buying the GBP Sterling amount they need, monthly. On the same day every month our client receives a confirmation from us, which tells them the rate of exchange we were able to achieve when we bought for them. In the same confirmation we invite the client to send us the appropriate base currency amount. Because of the way this process is structured, the amount of money our client sends us varies each month...but they don't mind.
On average, over the past 23 months, we have improved the client's rate of exchange (and therefore saved them) over 2.5%. We include the cost associated with sending a payment - a cost which their bank charges them separately - into the rate at which we exchange/buy their currency. All they need to do is send us the amount needed to settle the transaction.