Here's another simple number we should know but really don't: What's it cost to arrest somebody? Seems like it matters (at least to the taxpayer) if the choice is between a citation and an arrest.
Part of the problem in figuring this out is that the expense is divided between different departments, jurisdictions, and budgets (police, courts, sheriff, jail, prosecutor, and public defender). Another problem is there's not a simple turnstile that you pay to go through. There is some economy of scale, I would presume. In other words, reducing arrests by 10 percent would not cost the cost by 10 percent.
An article in the Arizona Republic today mentions some dollar figures. I'm not sure where they're from or how they were come up with, but here they are: "Bookings cost $192 per suspect and the city must pay about $72 per day for each inmate housed in county jails."
Now keep in mind Maricopa County is Sheriff Joe land and spends very little on jail. Rikers Island in New York City, by contrast, costs $190 per day. Regardless, jail figures are pretty easy to come up with because, well, they have a budget.
It's the booking cost that is more interesting and much harder to determine. Same with the cost of a court appearance. Still, for someone who spends a night or two in jail, the cost of each arrest is at least a couple hundred of dollars. Throw in a court appearance and we're probable pushing a grand.
[Anybody know if these figures are out there somewhere and I just haven't found them?]