During the 1989 Loma Prieta earthquake, a portion of the eastern section's upper deck collapsed onto the lower deck and the bridge was closed for a month. Reconstruction of the eastern section of the bridge as a causeway connected to a self-anchored suspension bridge began in 2002; the new eastern section opened September 2, 2013, at a reported cost of over $6.5 billion; the original estimate of $250 million was for a seismic retrofit of the existing span.
That's clearly just the first estimate. I bet the final cost is x3. Maybe even a lot more.
The SF Bay Bridge was a 2,500% budget overrun: from $250M to $6.5B.