The multi-agent cost formula
**The total cost of a multi-agent task has four components:** `total_cost = orchestrator_cost + Σ_workers(worker_loop_cost) + inter_agent_message_cost + synthesis_cost`. Each component is itself an LLM call (or loop) with its own input/output token bill. The orchestrator plans and routes; each worker executes; inter-agent messages carry context between calls; synthesis assembles the final output from all worker results.
**Orchestrator cost.** The orchestrator receives the full task description and outputs subtask assignments. On CrewAI, the manager LLM sees the full goal, the list of available agents with their role descriptions, and the current state — typically 2K-5K input tokens. It outputs a delegation decision: 200-500 tokens. On LangGraph supervisor, the supervisor node receives a shared state object (growing as workers report back) and outputs a routing decision. LangGraph supervisors are often more token-efficient because they operate on a structured state graph rather than natural-language plans.
**Worker loop cost.** Each worker runs its own agent loop — the same N-turn accumulation structure described in the agent loop cost calculator. For a 3-turn research worker with 5K average input per turn and 400 output tokens: 3 × 5K × input_rate / 1M + 3 × 400 × output_rate / 1M. On Sonnet 4.6: 15K × $3/1M + 1.2K × $15/1M = $0.045 + $0.018 = $0.063 per worker per task. For 3 workers: $0.189 just in worker execution.
**Inter-agent message cost.** Every time one agent passes output to another — worker result to orchestrator, subtask description from orchestrator to worker — those tokens are billed as input on the receiving agent's next call. In CrewAI's sequential delegation pattern, each worker output (~800 tokens) is included in the next agent's context. In a 5-worker chain: 4 × 800 = 3,200 tokens of inter-agent message overhead billed as input. On Opus 4.7: 3.2K × $15/1M = $0.048 extra per task from message passing alone.
**Synthesis cost.** After workers complete, the orchestrator (or a separate synthesis step) assembles the final output. On a research-and-write task, synthesis receives all worker outputs (~1.5K per worker for 3 workers = 4.5K tokens) plus the original task description (1K), emitting an 800-token final document: 5.5K × $3/1M + 0.8K × $15/1M = $0.0165 + $0.012 = $0.0285 on Sonnet 4.6. Small per-task, but synthesis is often run on a more expensive model to improve quality — running synthesis on Opus adds $0.0825 + $0.060 = $0.1425 instead.
**The formula simplifies to a multiplier.** Rule of thumb: a multi-agent task with N workers costs approximately (1.2 + N × 1.15) × single_worker_loop_cost. The 1.2 accounts for orchestrator overhead; the 1.15 per worker accounts for inter-agent message passing beyond the pure worker cost. This multiplier holds within ±15% for most production CrewAI and LangGraph deployments — it breaks down for very long worker loops (>8 turns) or large inter-agent payloads (>2K per message).