GPT-5.4 Mini vs Gemini 3.8 Flash: which API costs less?
Averaged across three realistic workloads, Gemini 3.8 Flash is about 11% cheaper than GPT-5.4 Mini. 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-5.4 MiniOpenAI | $0.750 | $4.50 | $0.075 |
| Gemini 3.8 FlashGoogle | $0.750 | $3.75 | $0.075 |
Gemini 3.8 Flash: Launch price until Dec 31, 2026; $1.50/$7.50 announced from Jan 1, 2027.
Monthly cost, side by side
| Workload | GPT-5.4 Mini | Gemini 3.8 Flash | Difference |
|---|---|---|---|
Customer-support chatbot 2M input + 0.5M output tokens/month, 60% of input served from prompt cache | $2.94 | $2.56 | Gemini 3.8 Flash −13% |
RAG / document Q&A 20M input + 1M output tokens/month, 70% cached (shared context) | $10.05 | $9.30 | Gemini 3.8 Flash −7% |
Agentic coding assistant 50M input + 5M output tokens/month, 80% cached (long sessions) | $33.00 | $29.25 | Gemini 3.8 Flash −11% |
Your traffic looks different? Run your own numbers in the calculator.
FAQ
Which is cheaper: GPT-5.4 Mini or Gemini 3.8 Flash?
Across three realistic workloads (chatbot, RAG, agent), Gemini 3.8 Flash works out about 11% cheaper than GPT-5.4 Mini on average. Raw rates: GPT-5.4 Mini $0.750/$4.50 per 1M tokens vs Gemini 3.8 Flash $0.750/$3.75. Verified 2026-10-17.
Does prompt caching change the comparison?
Yes — cached input costs $0.075 on GPT-5.4 Mini and $0.075 on Gemini 3.8 Flash. 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.