Real-time AI cost monitoring addresses the challenge of attributing LLM spend from providers like OpenAI and Anthropic, which deliver single-line invoices with no built-in breakdown. Traditional cloud tagging fails for dynamic AI workloads and shared model endpoints. The approach covered uses virtual tagging and unified billing (via Finout's MegaBill) to map costs to teams, features, and customers without code changes or native tag enforcement. Key metrics to track include cost per token, per request, per model, and per business dimension. ML-powered anomaly detection flags spend spikes in real time, and autonomous FinOps agents can investigate root causes. The guide distinguishes monitoring (visibility), management (governance), and optimization (efficiency) as sequential FinOps stages, recommending real-time or daily monitoring for active AI workloads and hourly visibility for agentic systems.