This is a linkpost for https://srconstantin.wordpress.com/2016/12/07/if-prison-were-a-disease-how-bad-would-it-be/
I didn't get that impression. Sarah wasn't stating: Here is a cost vs. benefit of Prisons. She was instead writing about how we could measure the costs of prison. If she doesn't write at all about benefits, there is no reason to infer that she is deliberately leaving them out to be misleading. Actually, I think this sort of inference towards what she is actually trying to say based on what you think she left out is misleading.
Gwern doesn't say anything interesting. He points out that you do, in fact, need to measure benefit for cost vs. benefit. I guess th...