A rationalist interjects: “You should make public predictions about this stuff!” Idk, should I? What should I make predictions about? About whether individual cases succeed, or some broader trends? I'm not sure if it’s worth my time. I really like $ as a metric, not sure what the predictions add. Very open to being convinced here!

Predictions about individual cases would be great. Whenever you take a deposit write down the condition for the bounty being paid out, the amount of the bounty, and your self-assessed likelihood of the person paying the bounty in the following twelve months to you into a public Google Sheet. Maybe, add another row for "time-spent with the person".

The exercise about thinking beforehand about how likely you will solve the issue for the person is useful for you to understand your method better. It also help informing potential customers well about what they can expect from your service. 

Finally, it would be great to have a one-year follow-up after a bounty is paid and that information also added to the Google Sheet.

What are the failure rates? So, I would love to share data on the cases I haven’t (yet) been able to help… but I don’t know how?

1) How many cumulative hours have you spent on things where there has been no success and you guys aren't working together anymore on the issue? How does this compare to the number of hours which have resulted in success, and the number where the result is tbd? How many hours have resulted in partial or incremental success, without meeting agreed upon win criteria?

2) Of those where someone bailed how many times did they bail and how many times did you bail? There's some ambiguity here, but probably manageable. If you don't expect to hear back (e.g. because it's been two months), then count it as a bail. If you suggest that their problem isn't in your wheel house and they say "okay" rather than asking to try anyway, I'd count that one as on you.

3) To what extent have you "failed" because the initial goal turned out to be meaningfully mis-specified? E.g. someone wants to be more socially active in a certain group, only to realize their aversion to socializing in that group is actually well grounded, and they no longer want to achieve their initial goal?

4) To what extent have you caused problems by being too successful for the specified goal? E.g. The person actually ends up active in that social circle before realizing that they've been wasting their time doing so. Or maybe you help someone be more secure and they're happy for it, but it did lead to them losing a relationship when they spoke a little too freely.

wow this is contraversial (my own vote is +6) 

wonder why

Amazing! This may have convinced me to go from "pay what you think it was worth" per session, to precommiting to what a particular achievement would be worth like you do here.

Please, tell me what metric I should use here!

Is it feasible to just generate a bunch of such metrics, with details about what was included or not included in a particular number, and share all of them?