Final answer:
High-frequency starting is the method for arc starting with GTAW that has the highest cost.
Step-by-step explanation:
The Gas Tungsten Arc Welding (GTAW) process can be started using different methods, each with its own advantages and disadvantages. One of the methods for arc starting in GTAW is called high-frequency starting. This method uses high-frequency current to ionize the air between the tungsten electrode and the workpiece, creating a conductive path for the arc to form. High-frequency starting is commonly used in industries where precise and clean arc starting is required, such as aerospace and nuclear power plants. However, this method tends to be more expensive due to the cost of the high-frequency equipment and the need for additional safety measures.