It cost me $30.00, I dont know if it is the same price everywhere, Im sure you can go to a vet and have it done even if you are not a customer, my vet suggested to have it done while he was being neutered.
The dog wears a tag stating he is marked and has a # and phone # in case he is found,, then you can take them to a vet or a dog pound they all have the scanners to scan them, then scanned it will bring up my info and he will be returned,, there was a case locally that a dog was stolen from someones yard,,, and later someone reported it, the police went with a scanner scanned the dog and it was returned!
I believe even if he is found and you call the phone # on the tag , they will locate the owner,, no scanner involved.