Find ‘em, arrest ‘em, kick ‘em out. This is Donald Trump’s elevator pitch for deporting millions of migrants in the country illegally.

Reality, as usual, is a lot more complicated. The United States has never deported more than 500,000 migrants in a single year — and Trump wants to go after as many as 13 million. Trump insists cost should be no object. “It’s not a question of a price tag,” the president-elect told NBC News recently. “We have no choice. They’re not staying here.”

Members of Congress might take a different view, including Trump’s fellow Republicans, who will control the Senate and House next year. To follow through on his plan, Trump is going to need Congress to provide the type of money that could fund entire agencies, at a time when the size of the national debt is already causing hiccups in financial markets.

Deporting an estimated 13 million undocumented migrants in the country could cost $315 billion, according to the American Immigration Council. For comparison, that would be six times the cost of the 2022 CHIPS Act meant to reboot semiconductor manufacturing in the United States.

Other estimates are higher. When Trump launched his first presidential bid, in 2015, the right-leaning American Action Forum pegged the cost of deporting all undocumented migrants in the country at $400 billion to $600 billion during a 20-year span. In 2024 dollars, that would be $540 billion to $810 billion.

“The promise of deportation is an extremely expensive one in terms of the budget required and the economic fallout," Douglas Holtz-Eakin, president of the American Action Forum, wrote on Nov. 8. “It would also rend the social fabric of America as it would be necessary to do house and business searches to find those who should be deported.”

Expelling unauthorized migrants is not just a matter of rounding them up and putting them on a plane back home. Authorities must first find them, verify their undocumented status, and turn them over to Immigration and Customs Enforcement. The American Immigration Council estimates the cost of arresting 13 million migrants at $89 billion.

The legal process requires a judge to formally order the expulsion of migrants. The government has to house migrants while they wait for a hearing. That would cost another $168 billion.

There’s nowhere near enough space to detain that many migrants. The total prison population in the United States is 1.9 million, at every level of government. So the government would have to build detention camps for millions more. This is why the stock price of companies that build private prisons has soared since Trump’s election.