From the article: > The total cost for installing full-height gates in just those 128 stations would be over $7 billion, the agency found, and half-height gate

From the article: > The total cost for installing full-height gates in just those 128 stations would be over $7 billion, the agency found, and half-height gates would cost $6.53 billion. Once installed, the agency would have to spend more than $119 million each year to maintain the doors.