Beyond the costs of a mass detention and expulsion of undocumented immigrants, what would the long term impact be? Numbers high enough to guarantee another recession or even a depression. Via the Center For American Progress:
"...legalization of undocumented immigrants and more flexible immigration channels would significantly expand the economy—by a cumulative $1.5 trillion in gross domestic product over 10 years—through increased consumer spending, higher tax receipts, and other related factors. A deportation approach, by contrast, would have the cumulative effect of draining $2.5 trillion over 10 years from the U.S. economy. That is a $4 trillion swing in GDP depending on which policy approach we adopt." EMPHASIS OURS
The right wing's dream solution to the issue would collapse us.