A nightly batch job uses Batch API AND prompt caching. What is the effective cost multiplier vs standard sync calls (cache hits, batch discount)?
Answer: ~5% (cache and batch stack)
Cache reads stack with batch discount: ~10% (cache hit) × 50% (batch) = ~5% of the standard sync input rate. This combination is the largest single cost lever for high-volume non-interactive workloads with stable system prompts.