Say $50,000 per inmate/ per year/ times “58,766 known or suspected” aliens in the custody of federal authorities” — all paid for by American taxpayers and you get a BIG FAT NUMBER...
How much does it cost to send someone to prison?
https://www.marketplace.org/2017/05/15/world/how-much-does-it-cost-send-someone-prison
From link:
According to the Vera Institute of Justice, incarceration costs an average of more than $31,000 per inmate, per year, nationwide. In some states, it’s as much as $60,000. Taxpayers foot the bill for feeding, housing and securing people in state and federal penitentiaries.May 19, 2017
Cheaper just to hang them.