One of the first things that you will notice about the services of a quality Medfield mobile locksmith is that the cost will always vary from time to time. The first thing that will determine the cost of the services you will get is the time when you are calling for help. Ideally, you will end up spending more when you need help on an emergency basis than if you were looking for a locksmith during normal hours. The reason for this is because they often have to go out of their way to be able to assist you, especially at odd hours.