New York is indeed an expensive place, but experts say that alone doesn’t explain a recent report that found the city’s annual cost per inmate was $167,731 last year—nearly as much as it costs to pay for four years of tuition at an Ivy League university.

They say a big part of it is due to New York’s most notorious lockup, Rikers Island, and the costs that go along with staffing, maintaining and securing a facility that is literally an island unto itself.