The heart of Donald Trump's immigration plan would cost a lot of money

The flashiest part of Donald Trump's immigration plan might be the proposed erection of a wall along the US-Mexico border.

But it would likely be far from the most expensive part of a plan that could run a tab in the hundreds of billions.

Though his platform doesn't explicitly lay out what he'd propose to do with immigrants not authorized to live in the United States, Trump suggested in an interview with "Meet the Press" host Chuck Todd that he would move to deport all of the approximately 11 million immigrants living in the country without proper authorization.

"We will work with them," he said when asked by Todd if he was going to "break up families."

"They have to go. Chuck, we either have a country or we don't have a country."

But that wouldn't come cheap. National Journal's Lauren Fox laid out the math on Trump's plan Tuesday.

One report, released in 2010 by the left-leaning Center for American Progress, estimated that it would cost $200 billion to "to enforce a federal dragnet that would snare" immigrants unauthorized to live in the United States.

However, that calculation used figures from 2008, which estimated the number of unauthorized immigrants living in the United States at 10.8 million. A more recent estimate, from the non-partisan Pew Research Center, pegs the number at 11.3 million, about half of whom came from Mexico.

Another recent estimate calculated that the cost of deportation would be disastrous for the US economy. According to the right-leaning American Action Forum, it would take between $400 billion and $600 billion to deport 11 million people without proper documentation over 20 years.

That estimate doesn't take into account the cost of enforcement to prevent return, which could reach upward of $300 billion. Such mass deportation would take 6.4% of US workers out of the country, according to the AAF report. With them would depart approximately $1.6 trillion in wages, spending, and other economic activity, more than the GDP of Texas. The agricultural industry would be disproportionately effected by the move - half of the US' farm workers in the past 15 years have been undocumented.

These estimates don't take into account the approximately $15 billion that undocumented immigrants contribute to Social Security, according to Stephen Goss, chief actuary for the Social Security Administration.

Then there's the matter of Trump's biggest real-estate plan: the wall. Trump has said that he plans to make Mexico pay for it, but Mexico has said it won't.

Whoever's paying would have to pick up a significant tab: National Journal estimates its cost at about $6.4 billion. The US already has 650 miles of fencing, according to National Journal. But Trump's plan calls for a stronger one along all of it, which Fox estimates to be 1,989 miles. (A US Geological Survey report estimated the US-Mexico border's length is 1,933 miles.)

For his part, Trump said in his policy paper that if Mexico doesn't pay for the wall, he'd raise the money by increasing the fees on temporary visas from Mexican diplomats, executives, and North American Free Trade workers, as well as considering cutting foreign aid and raising tariffs. He has also dismissed questions about the cost of his plan as a whole.

"The cost of doing it? Look at the cost of what we have right now," he said on "Meet the Press" Sunday.

Trump's immigration plan - so far his only official policy paper - prioritizes the wall, deportation, cracking down on visa overstays, a digital verification program for workers, and ending citizenship for children of undocumented immigrants born in the United States.

His paper disparages what he calls the "Schumer-Rubio bill" - an ambitious immigration reform plan spearheaded by a bipartisan "Gang of Eight" senators that crumbled two years ago - as "nothing more than a giveaway to the corporate patrons who run both parties."