According to the Center for American Progress (pdf document) it would cost $41 billion per year (over 5 years) to remove illegal immigrants.
I have no idea if this number is too high, too low, or about right. The study does have some numbers backing it up, but again I have little way judging the numbers in terms of drawing inferences as to the costs of massive deportation.
Recent reports of worksite enforcement, however, offer a useful indicator of average apprehension costs. We extrapolate from the available evidence to provide an estimate of the per-apprehension cost. In 1999, 240 agents apprehended 2,849 unauthorized workers, and, as noted above, 90 agents apprehended 445 unauthorized workers in 2003.28 Assuming a typical annual cost of $175,714 per agent,29 and after summing the number of apprehensions (3,289) and agents (330), the average apprehension cost comes to $17,603. Assuming a 20% voluntary departure rate, the total costs for apprehending 8,000,000 undocumented immigrants would be $141 billion over five years. (Using the same average apprehension figure, apprehending 9,000,000 immigrants would cost $158 billion over five years.)
Is 20% voluntary departure realistic? Is it too high or too low? We really have very little information to go on. As such this study is pretty much a guess. Still, I’m pretty sure that the cost of deporting millions of illegal immigrants would be large. Also, there are other factors to consider. For example, immigration is probably one of the reasons why Social Security isn’t as bad off as it otherwise might be. Also, removing several million workers from the work force would likely have an adverse impact. Sure wages would go up, but unless prices go up to cover these higher costs (and they can’t, at least not in all cases) then some (many?) firms will have to shut down.
