Claude Opus 4.8 vs GPT-5.5: which API costs less?
Averaged across three realistic workloads, Claude Opus 4.8 is about 11% cheaper than GPT-5.5. Below: raw rates and side-by-side monthly costs, computed from prices verified 2026-10-17 (we track what you are billed today, promos included).
Rates per 1M tokens
| Model | Input | Output | Cached input |
|---|---|---|---|
| Claude Opus 4.8Anthropic | $5 | $25 | $0.500 |
| GPT-5.5OpenAI | $5 | $30 | $0.500 |
Claude Opus 4.8: Previous generation; Opus 5.5 is 20% cheaper. GPT-5.5: Prompts up to 272K tokens; longer prompts cost more.
Monthly cost, side by side
| Workload | Claude Opus 4.8 | GPT-5.5 | Difference |
|---|---|---|---|
Customer-support chatbot 2M input + 0.5M output tokens/month, 60% of input served from prompt cache | $17.10 | $19.60 | Claude Opus 4.8 −13% |
RAG / document Q&A 20M input + 1M output tokens/month, 70% cached (shared context) | $62.00 | $67.00 | Claude Opus 4.8 −7% |
Agentic coding assistant 50M input + 5M output tokens/month, 80% cached (long sessions) | $195 | $220 | Claude Opus 4.8 −11% |
Your traffic looks different? Run your own numbers in the calculator.
FAQ
Which is cheaper: Claude Opus 4.8 or GPT-5.5?
Across three realistic workloads (chatbot, RAG, agent), Claude Opus 4.8 works out about 11% cheaper than GPT-5.5 on average. Raw rates: Claude Opus 4.8 $5/$25 per 1M tokens vs GPT-5.5 $5/$30. Verified 2026-10-17.
Does prompt caching change the comparison?
Yes — cached input costs $0.500 on Claude Opus 4.8 and $0.500 on GPT-5.5. Our scenario numbers already include realistic cache hit rates.
Is cheaper always better?
No. Price is one axis — model capability, context window and latency differ. This page answers only the cost question; benchmark quality on your own tasks before switching.