Self-pay jail

I heard a mention of this during a news story about Paris Hilton starting her jail term and went online to try to find out more. The NY Times ran a story about this in late April, but it's no longer free on their website (since it's more than 30 days old). I don't know how this can be legal and I certainly don't know how this can be justified - inmates pay around $100 a day for special priviledges and improved living conditions.

http://www.talkleft.com/story/2007/4/28/22548/1548