How much $ do you expect for a professional locksmith to go to you for service?
The "Service Charge" or "Trip Charge" is what it will cost for the locksmith to come to you.
Remember they need to pay for their time, wear and tear on the service vehicle, and insurance.
With this in mind, what do you as a consumer think a reasonable charge should be?
If they advertise ...
0-3 miles from you.
3-5 miles
5-10 miles
10+