Palantir (PLTR) chairman and venture capitalist Peter Thiel just put $3 million on the table to fight California's proposed wealth tax targeting billionaires. And if you think that's expensive, wait until you hear what the tax itself would cost.

Thiel made the donation to the California Business Roundtable on December 29, according to financial disclosures reported by the New York Times. Silicon Valley insiders expect this to be just the opening salvo, with more tech money likely to follow.

Here's what they're fighting: a ballot initiative backed by a state health care union that would slap a 5% annual tax on the assets of California residents worth over $1 billion. The stated goal is offsetting federal budget cuts hitting the state's healthcare system. The measure needs nearly 900,000 signatures to make it onto the November ballot.

Newsom Says the Tax Is Already Backfiring

Governor Gavin Newsom isn't waiting around to see what happens. He told the New York Times on Monday that he plans to kill the measure, arguing that just the threat of it has already done damage by pushing billionaires toward the exits.

And the exodus appears real. At least six billionaires have already left California, according to Bloomberg. Google co-founders Larry Page and Sergey Brin, along with Thiel himself, are reportedly weighing whether to cut or reduce their California ties.

Venture capitalist Chamath Palihapitiya and hedge fund billionaire Bill Ackman have both sounded alarms, warning the tax could crush entrepreneurship and innovation in the state.

For Thiel, this $3 million check represents his largest disclosed political contribution in years. For context, he dropped over $35 million backing Make America Great Again candidates during the 2022 midterms.

While the donation isn't technically earmarked specifically for fighting the ballot measure, the New York Times reports it will fund the lobbying group's broader campaign against what it considers anti-business policies.

Thiel didn't respond to requests for comment.