Token fees are the most visible cost component. An agent that runs for several hours on a complex task may consume millions of tokens — at typical API pricing, a session can easily cost $5-50 depending on the model used and the task complexity. Multiply this by a fleet of agents running concurrently across many tasks and the monthly bill becomes significant.
Less visible costs include: developer time spent reviewing agent output (which scales with the number of agents and the quality of their work), the cost of mistakes (a merge that introduces a bug requires engineering time to diagnose and fix), and operational overhead (monitoring agent health, managing API keys, handling quarantine events).
Cost optimization strategies include: using smaller, cheaper models for tasks that do not require maximum capability; setting token budgets to prevent runaway sessions; batching related tasks so agents reuse loaded context rather than starting fresh; and measuring output quality per dollar to identify which model/task combinations are cost-effective.