The cost has skyrocketed from an initial $650 million in 2003 to more than $1.5 billion today, and that's just the beginning of the cost overruns.
In the face of vocal opposition to the $1.6 billion subway that would create jobs and ease crowding on Chinatown buses, community and labor leaders rallied in support of it at City Hall.
"It's in neighborhoods where our buses crawl along Stockton Street at 3 miles per hour," said Supervisor David Chiu.
Chiu says he's heard some people who are against it.
"I've heard some people who, all of a sudden against this project, call it a 'subway to nowhere,'" said Mayor Ed Lee. "Well, I don't think Chinatown is nowhere. I don't think South of Market is nowhere."
But Lee has found over the past week that some of his opponents in his race for re-election disagree.
"Historically, I was supporter of the Central Subway project when it was $650 million," said City Attorney Dennis Herrera. "Now it's ballooned to $1.6 billion."
Candidate Herrera's remarks put subway supporters on the defensive, even as they held a press conference to announce they have the money to start digging.
Though tunneling won't begin for a few months, there's already lots of digging happening in Union Square just to move the utility lines out of the way. But critics say, although this puts a lot of people to work, they'd rather see the money spent to improve bus service instead.
"The financing of this project -- if they build it -- makes Muni worse off than it already is," said Matt Williams with the Sierra Club.
Williams is worried the cost to run the subway will run Muni deeper in the hole and says the design -- without a stop right at Market Street -- is a bust.
"If we're standing here on the Market Street stop, which is in Union Square, it tells you that to transfer to everything that's on Market Street, it's going to take a lot longer than if you just stayed on the bus," said Williams.
Supporters insist, though, that the walk isn't that far and would let you avoid the gridlock in the city.