“What’s the cost of deporting every single one?”
There is no need to deport ‘every single one.’ All we need to do is show a willingness to deport and to not tolerate violations of our immigration law. Much like enforcing a speed limit. Police do not need to catch all people speeding but make it likely that one will get ticketed and delayed enugh to make attempting to speed a bad proposition.
If we do have a need for exogenous unskilled labor (which I don’t believe we do but am open to the proposition), I’d prefer that it only be open to people who have not previously not violated our immigration and labor laws.
IMO There will be a large economic expense to an amnesty but the biggest expense of an amnesty will be the message that the rule of law in the US means nothing and that those who cheat will prosper.