I understand if you have offline computers. I understand if the computer needs to be behind a plexiglass wall and the mouse and keyboard need to be chained down. But quickly these will pay for themselves. Data Entry pays significantly more, I imagine there are plenty of white collar criminals with tech skills that could make $30-$100/hr.
Even if you only let the inmate keep 20%, the inmate is getting skills, money, the system is getting extra money, the company getting the data entry is getting cheap labor.
I can't see too many downsides other than the initial set up cost. Pretty sure the right side of the aisle will see the $$$ and approve. The left side should also see the $, but also know how humane and potentially rehabilitating.