Google: Nano Banana 2 (Gemini 3.1 Flash Image) vs xAI: Grok 4.20
Head-to-head API pricing and cost comparison between Google’s Google: Nano Banana 2 (Gemini 3.1 Flash Image) and xAI’s xAI: Grok 4.20. Prices auto-refresh daily from OpenRouter.
Google: Nano Banana 2 (Gemini 3.1 Flash Image) is 60% cheaper for input tokens; xAI: Grok 4.20 wins on output tokens at $2.50/1M.
Side-by-side comparison
| Spec | Google: Nano Banana 2 (Gemini 3.1 Flash Image) | xAI: Grok 4.20 |
|---|---|---|
| Input price (per 1M) | $0.50 | $1.25 |
| Cached input (per 1M) | — | $0.20 |
| Output price (per 1M) | $3.00 | $2.50 |
| Batch input (per 1M) | — | — |
| Batch output (per 1M) | — | — |
| Reasoning price (per 1M) | — | — |
| Context window | 131K | 2000K |
| Vision support | Yes | Yes |
| Caching support | No | Yes |
| Batch API | No | No |
| Reasoning capability | No | No |
Monthly cost at volume
Estimated monthly API spend at common production traffic levels (input/output tokens per request shown).
| Volume | Google: Nano Banana 2 (Gemini 3.1 Flash Image) | xAI: Grok 4.20 | Savings |
|---|---|---|---|
1K req/day 500in / 200out tokens | $25.50 | $33.75 | $8.25 Google: Nano Banana 2 (Gemini 3.1 Flash Image) wins |
10K req/day 1500in / 500out tokens | $675.00 | $937.50 | $262.50 Google: Nano Banana 2 (Gemini 3.1 Flash Image) wins |
100K req/day 3000in / 800out tokens | $11,700 | $17,250 | $5,550 Google: Nano Banana 2 (Gemini 3.1 Flash Image) wins |
1M req/day 8000in / 2000out tokens | $300,000 | $450,000 | $150,000 Google: Nano Banana 2 (Gemini 3.1 Flash Image) wins |
Adjust input/output token counts, request volume, batch & cached pricing.
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Frequently asked questions
Which is cheaper, Google: Nano Banana 2 (Gemini 3.1 Flash Image) or xAI: Grok 4.20?
For input tokens, Google: Nano Banana 2 (Gemini 3.1 Flash Image) is roughly 60% cheaper at $0.50/1M vs $1.25/1M. For output tokens, xAI: Grok 4.20 wins at $2.50/1M. Real-world cost depends on your input/output ratio — use the calculator to model your actual workload.
What’s the context window difference?
Google: Nano Banana 2 (Gemini 3.1 Flash Image) has a context window of 131K tokens. xAI: Grok 4.20 offers 2000K tokens. Larger context windows are valuable for long documents, RAG pipelines, and multi-turn conversations — but they come with higher input-token bills if you fill them every request.
Should I use Google: Nano Banana 2 (Gemini 3.1 Flash Image) or xAI: Grok 4.20?
Choose Google: Nano Banana 2 (Gemini 3.1 Flash Image) if you’re already on the Google stack, want broad ecosystem support, or prefer its lower input price. Choose xAI: Grok 4.20 for xAI’s ecosystem, native vision input, or its cheaper output tokens. Run a small benchmark on your own prompts before committing — price is only one axis.
How are these prices kept current?
Prices are pulled directly from OpenRouter’s public models API once every 24 hours via a Convex cron job, then normalized to per-1M-token figures. Last refresh: Jun 19, 2026.