Here's a classic infrastructure debate: should you spend $120 billion on a high-speed rail line, or should you let Elon Musk dig a tunnel for less than 5% of that? Musk, the CEO of Tesla Inc. (TSLA), is making the case for option B.

On Wednesday, Musk took to X to criticize California Governor Gavin Newsom's High Speed Rail project connecting Los Angeles and San Francisco. "The @BoringCompany could build a Hyperloop tunnel from downtown SF to downtown LA for <5% of this [$120 billion] cost," Musk wrote, quoting a post that suggested the same money could fund free flights between the cities for 200 years. He added that such a tunnel "would be a technological marvel exceeding any high speed rail on Earth."

This isn't Musk's first swipe at the project. He previously alleged it was riddled with fraud after California's Transportation Secretary, Adetokunbo "Toks" Omishakin, indicated the undertaking would need over $126 billion in additional funds. "It's all going to fraud and bureaucracy," Musk said at the time.

Governor Newsom, for his part, is standing by the rail. He reaffirmed that the project is necessary for the state, noting that over 463 miles of the 494-mile route are ready for construction. He also touted the creation of over 16,000 jobs and defended the project's financial integrity, confirming it has passed all auditing checks.

The high-speed rail has critics beyond Musk. The administration of President Donald Trump previously withdrew over $4 billion in funding for the project—a move challenged in California court but ultimately upheld. Trump's Transportation Secretary, Sean Duffy, has also criticized the project, slamming its "monstrous $135 BILLION price tag" and noting that over $16 billion of the funding comes from American taxpayers.

Meanwhile, Musk's Boring Company is pointing to its recent work in Las Vegas as proof of concept. The company claimed its Vegas underground loop moved over 82,000 passengers during the CONEXPO-CON/AGG construction trade show early last month, helping people get to and from expos in the city. So while California debates a $120 billion rail, Musk is essentially saying: "Hey, I could dig you a really cool tunnel for a fraction of that. And look, my tunnels work!" It's a bold claim that puts a fresh spotlight on one of America's most expensive—and controversial—infrastructure projects.