In 2008, New York's Department of Correction's budget was $978 million ($939 million of which is paid for city tax dollars). "In Fiscal 2007, the Department handled over 100,000 admissions, managed an average daily population of 13,987 and transported 326,735 individuals to court." The average length of stay is 47 days.
That's $70,000 per inmate per year. Or $190 per person per night. I think it's safe to say that Rikers Island is the world's most expensive jail.
You could say that Rikers gives you and a friend a double room for $383 night. But you don't get to pick your friend. Meanwhile I can get a double room tonight at the Holiday Inn on 57th Street in Manhattan for $268. But the Holiday Inn doesn't have the coveted LaGuardia view.
You can see the DOC budget here.