That figure comes from one advocacy group and gets there by counting the schooling of US-citizen children as a cost of illegal immigration, then crediting those same citizens' taxes to somebody else.

The number is FAIR's 2023 study: $182 billion in gross costs, minus $31 billion in taxes, for a net $150.7 billion. Its single largest line is $78 billion in K–12 education — and that line covers 5.4 million US-citizen children, most of them born here, who are entitled to a public education under Plyler v. Doe the same as any other American child.

That produces an accounting rule that cannot be applied consistently. A US-born child of undocumented parents is charged to the immigration ledger while in school; the taxes that same person pays for the next forty years are credited to the citizen ledger. Cost on one side, revenue on the other, same human being. Economists also treat schooling a child as an investment that returns higher earnings and higher taxes, not as money set on fire.

Then there is the revenue side. The study allows $31 billion in taxes paid. ITEP, measuring the same population, found $96.7 billion. The Cato Institute's review concluded the report overstates costs, undercounts revenue, inflates the size of the population, counts US citizens as illegal immigrants, and uses a cost-estimation method the peer-reviewed literature rejects. Every group named here has a policy position — which is exactly why the method matters more than the headline.