If US taxpayers have to pay to deport an illegal over 16 years of age, the violator of US immigration policy of any citizenship will face a permanent U.S. travel ban.
This would incentivize current non-citizen residents to EITHER proactively seek legal immigration status citizenship/ naturalization/ work visa OR leave the US of their own accord and expense.
The American Deportee Lifetime No Fly list would be shared with Interpol and airlines so that non-Americans who violated U.S. immigration laws could never enter the US ever again practically or legally.
Another complimentary policy would be to eliminate automatic citizenship for children born in the U.S. to non-citizen parents.
Estimated deterrence savings: $5 trillion in welfare expenses and homeland security. Especially by eliminating birthright citizenship, you’d see a huge reduction in immigrations.
The total conservative cost of mass deportations according to the American Immigration Council will be $315 billion.