GPT-6.1 Sol vs GPT-6 Luna: which API costs less?
Averaged across three realistic workloads, GPT-6 Luna is about 95% cheaper than GPT-6.1 Sol. 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 |
|---|---|---|---|
| GPT-6.1 SolOpenAI | $2 | $10 | $0.100 |
| GPT-6 LunaOpenAI | $0.100 | $0.500 | $0.010 |
Monthly cost, side by side
| Workload | GPT-6.1 Sol | GPT-6 Luna | Difference |
|---|---|---|---|
Customer-support chatbot 2M input + 0.5M output tokens/month, 60% of input served from prompt cache | $6.72 | $0.342 | GPT-6 Luna −95% |
RAG / document Q&A 20M input + 1M output tokens/month, 70% cached (shared context) | $23.40 | $1.24 | GPT-6 Luna −95% |
Agentic coding assistant 50M input + 5M output tokens/month, 80% cached (long sessions) | $74.00 | $3.90 | GPT-6 Luna −95% |
Your traffic looks different? Run your own numbers in the calculator.
FAQ
Which is cheaper: GPT-6.1 Sol or GPT-6 Luna?
Across three realistic workloads (chatbot, RAG, agent), GPT-6 Luna works out about 95% cheaper than GPT-6.1 Sol on average. Raw rates: GPT-6.1 Sol $2/$10 per 1M tokens vs GPT-6 Luna $0.100/$0.500. Verified 2026-10-17.
Does prompt caching change the comparison?
Yes — cached input costs $0.100 on GPT-6.1 Sol and $0.010 on GPT-6 Luna. 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.