I'm rather surprised that the concept (and practice) of private prisons hasn't been taken up on some basic levels. Critically, private industry's singular motivation to enhance the "bottom line" runs counter to their maintaining any other goals, including humane treatment, rehabilitation (and thus reduction in prison population), access to legal resources, and more.

Where is the oversight? Where is the accurate accounting of costs and value?

taken up = legally questioned
because it is clearly wrought with basic conflicts of interest.