Currency markets are extremely volatile, and pricing literally changes from second to second. Some financial institutions generally maintain the same price all day, it is for small amount of funds, (less than $1000) and are priced significantly far away from the actual market to compensate for any movements. For larger amounts, pricing is based of current markets and will change in tandem with market movements. If you have built a good relationship with your FX advisor, they may hold the rate for the day on your behalf.