LLM judge cost is the share of your eval bill spent grading agent output instead of producing it. To control it, run a 40-line offline pre-gate that triages every span with four deterministic rules and escalates only the uncertain tail to the expensive judge. On one trace this cut judge cost share from 50% to 16%. LLM judge cost is the line item nobody puts on the FinOps dashboard. You add an LLM-as-judge to grade every agent span, you sleep better, and three weeks later the eval layer is ...