The 47th agent is when finance shows up. Below 30 agents in production, the Anthropic invoice is one tolerable line item somewhere south of $25,000 a month, and nobody asks who is spending what. Past 30, the line item crosses $25k. By 47, the median fleet I see at ZopDev customers is at $80,000 a month, and finance walks into the next budget review with a single question: which agent. Nobody can answer it. The cost dashboard buckets spend by AWS account, by team, by service, by tag. None of those buckets contain agents, because agents do not consume resources tagged with their identity. They consume tokens, charged on a single Anthropic or OpenAI account, with the per-call invoice opaque to the cloud cost system. Resource tags catch infrastructure. They miss the LLM bill entirely. The fix is a cost ledger: a five-field row per LLM call that the agent runtime stamps on the way out, paired with the existing MCP tool-call audit log.…