Off the top of my head:

    - prisons create high paying jobs in rural areas
    - private prison companies like Vanguard are quite lucrative (and Vanguard just happens to have former Vice Pres. Cheney as a major investor)
    - prison labor is drastically cheaper than minimum wage

There's more. Here's a decent article on the topic from Vice: http://www.vice.com/read/whos-getting-rich-off-the-prison-in...