In many cases, the programming from an existing transponder key can be copied to a new key, creating a duplicate. Because most cars use a rolling code that changes with each key turn, the vehicle must be present in order to clone the key.
Some keys cannot be cloned this way. In these situations, the car must be programmed to accept a new key. Proximity keys and keys that have buttons at the top must be programmed. Pricing can be found below.