The cost of deportation:  
"Each deportation conducted by ICE cost taxpayers an average of $10,854 in fiscal 2016, an official from the agency told CNNMoney. This amount includes everything from housing and feeding a detainee to transporting him back to his home country...."  
http://money.cnn.com/2017/04/13/news/economy/deportation-costs-undocumented-immigrant/index.html
There are approximately 11,000,000 undocumented people in the USA.  This includes many people from Europe: "The Pew Research Center estimates that there are 475,000 to 500,000 unauthorized immigrants from Europe in the United States, including around 50,000 in New York City...."
http://gothamist.com/2017/01/09/undocumented_immigrants_nyc.php

Deport them all, right?