The showmanship and publicity causes pressure on other manufacturers to pay that much. Otherwise, anybody working at a competitor will just be thinking to themselves "I'm just working here to get experience so I can have an edge on other applicants at Ford." Competitors that pay less will be dealing with high turnover unless they match Ford's wages.
And it's not just car companies that have to match wages. Other industries will have to keep up. And once everybody is making decent money, you have more customers.