The difference is not really the price
It is where the work happens. A dealership needs the vehicle brought to it. If you have no working key, the vehicle does not drive there — which means a tow truck is part of the plan before anybody has started on the key itself.
A mobile auto locksmith comes to the car. Driveway, street, shopping centre car park, apartment basement. The car stays where it is.
That is the honest comparison. No prices are published on this site, and any figure quoted from a web page for your specific make, model and year would be a guess.
What both options will ask you for
- Photo ID.
- Proof the car is yours — registration papers, or the vehicle registered in your name.
- The make, model and year. This decides everything about what equipment is needed.
- Where the car actually is.
When the dealership genuinely is the right answer
It happens, and pretending otherwise would be dishonest. Some vehicles need manufacturer-held security codes or dealer-only equipment for certain key operations, particularly on newer premium European models and in all-keys-lost situations on a handful of makes.
You should hear that on the phone, before anybody drives to you. If a job turns out to need the dealer, being told at the kerbside after a callout is a bad outcome for everyone.
The bit worth doing before you ring anyone
Check the obvious. A car that will not start is not always a key problem — a flat battery presents very similarly from the driver's seat, and so does a failing starter. And check whether a spare exists somewhere you have forgotten: a drawer, a partner's bag, the original dealer folder.
Afterwards: delete the old key and cut a spare
Two things worth insisting on once the new key works. Have the lost key deleted from the vehicle's memory, so whoever finds it is holding a piece of metal. And have a second key cut while the equipment is already there and the car is already open.
Originating a key with none in existence is a bigger job than duplicating one you already have. The moment you have exactly one key is the moment to fix that.