In my work representing Florida Sheriffs I am very familiar with how this really works. The statute allows a county for example to recover $50 per day of an offender's sentence. The statute also allows the Sheriff to assert the right to recover the fee as a counterclaim for a civil claim by the inmate.
For example, we have inmates suing over slip and falls in the jail. We counterclaim for costs of incarceration to offset it. I can tell you a lot of them are not very bright. These common areas of cells are on video. We've had a couple obviously set up the slip and falls and it's pretty obvious. Have one now where two inmates are at a table and one gets up and walks away, then with this exaggerated action "slips and falls." His accomplice then casually spilled water in the area.
Not saying they are all like that, but you have to realize that a substantial majority of the people in jail are, in fact, criminals and willing to take advantage and lie whenever they can make a buck.
I have no problem asserting counterclaim against them.
I've also never in 25 years, heard of a Sheriff actually collecting a cent of it, by targeting those who can pay or otherwise.
Many things to complain about with criminal justice system. I agree on drug offenses for example. This ain't one of them.