How much does prompt injection defense cost per request?

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2026 cost landscape, per request, at moderate scale: - **Heuristics only** (InjectShield OSS heuristic layer, Rebuff, LLM Guard, regex DIY): **free**, ~1 ms latency, runs on your hardware. Catches naive attacks; misses semantic. - **Small-LM classifier** (Llama Guard, Prompt-Guard-86M, fine-tuned DeBERTa): **~$0.0001-$0.001** depending on whether you self-host or call a hosted endpoint; 20-100 ms latency. Good direct-injection coverage. - **Anthropic Haiku semantic** (InjectShield's default semantic layer): **~$0.0002/request** at current Haiku pricing for short inputs; 100-300 ms latency. Strong semantic coverage including indirect/multi-turn. - **GPT-4 / Opus-tier classifier**: **~$0.01-$0.05/request**; 500-2000 ms latency. Overkill for input scanning. - **Lakera Guard / Prompt Armor (managed SaaS)**: enterprise pricing, typically per-MAU or annual contract — often **$10k-$100k+/yr** minimums; sub-100 ms latency. InjectShield's hybrid mode runs heuristics on 100% of traffic (free) and only escalates the ~5-15% of ambiguous traffic to Haiku — average effective cost is typically **under $0.00005/request**, two-to-three orders of magnitude cheaper than a Lakera contract while catching the same semantic class of attacks.