Turns out that Shapiro’s “expert” estimate of the cost of mass deportation is off by a factor of at least 4 (and probably much more), according to the right wing American Action Forum: Deporting 11 Million People Could Cost $400-600 Billion, Study Finds.

And the overall cost to the economy would be truly gigantic.

The study, which the American Action Forum plans to publish later on Friday, tests a rather straightforward proposition frequently offered by opponents of comprehensive immigration reform: How much would it cost to “immediately and fully enforce current law”—that is, to deport all undocumented immigrants while preventing another wave of people from entering illegally?

The answer, researchers found, is quite a lot, both to taxpayers and the economy more broadly. Removing all 11.2 million undocumented immigrants, both forcibly and through Mitt Romney’s infamous “self-deportation” policy, would take about 20 years and cost the government between $400 billion and $600 billion. The impact on the economy would be even larger, according to the study: Real GDP would drop by nearly $1.6 trillion and the policy would shave 5.7 percent off economic growth. Researchers Laura Collins and Ben Gitis also write that their estimates are conservative, since they do not include, for example, the cost of constructing new courts, prisons, and other buildings that might be needed to process and detain millions of immigrants.