An ICE spokesman said it does not detain unaccompanied children. However, it does oversee "juvenile facilities," managed by local jurisdictions, that allow for "temporary housing of children separate from adults." The average bed rate for this type of facility is $139.40 per day, according to ICE.
However, ICE estimates often lack in transparency and don't reflect the true cost. There's been so much discrepancy that the U.S. Government Accountability Office looked into ICE's budget requests and found that its methodology was inaccurate and recommended a change in the way it comes up with its cost estimates.
And then there's the question of how long immigrants are detained. ICE estimates an average stay of 44 days, but thousands of immigrants have been held far longer. In one case heard by the Supreme Court, an immigrant spend three years in detention.
The DHS projects there will be an average of 51,379 people held in immigration detention centers each day in fiscal 2018, a sizable jump from the last few years, which have hovered near the low 30,000s.
The increase stems follow's President Donald Trump's hardline policy against illegal immigration.