BART news release:
Thanks to a revised schedule, and an accelerated monthly delivery rate of new rail cars, the project is expected to cost $394 million less than when the contract was awarded in 2012.
[...]
The original contract awarded for 775 cars forecast a project cost of $2.584 billion but an October 2023 financial update lowered the forecast by 15%, to $2.190 billion. Over the course of 11 years, BART and the manufacturer, Alstom, have increased the pace of making and delivering the cars, resulting in significant savings.