High-volume, cost-sensitive work
Choose Grok 4.20 Reasoning
Grok 4.20 Reasoning costs 22% less on a typical mix of three input tokens for every output token ($1.56 against $2.00 per million tokens).
GPT-6.1 Terra vs Grok 4.20 Reasoning: price, context and capabilities
Choose GPT-6.1 Terra for reused prompts and documents (RAG, agents) and the latest release. Choose Grok 4.20 Reasoning for high-volume, cost-sensitive work and writing and code generation.
In short
- Grok 4.20 Reasoning is 22% cheaper than GPT-6.1 Terra at the headline price ($1.56 / 1M tokens vs $2.00 / 1M tokens).
- GPT-6.1 Terra reads more per request: 1.05M tokens against 1M.
- GPT-6.1 Terra is the newer model (Oct 26, 2026, against March 2026).
- Only Grok 4.20 Reasoning offers batch api.
Which should you choose?
Each answer below comes straight from the published prices, specifications and independent benchmark results.
Writing and code generation
Choose Grok 4.20 Reasoning
Grok 4.20 Reasoning charges $2.50 per million output tokens, against $5.00 for GPT-6.1 Terra. Output dominates the bill when answers are long.
Reused prompts and documents (RAG, agents)
Choose GPT-6.1 Terra
GPT-6.1 Terra charges $0.05 per million cached input tokens, against $0.20 for Grok 4.20 Reasoning.
Latest release
Choose GPT-6.1 Terra
GPT-6.1 Terra is the newer release (Oct 26, 2026, against March 2026 for Grok 4.20 Reasoning).
Monthly cost at three volumes
| Volume | GPT-6.1 Terra | Grok 4.20 Reasoning | Difference |
|---|---|---|---|
| Prototype: 1M input, 250K output tokens | $2.25 | $1.88 | Grok 4.20 Reasoning, $0.38 less |
| Production: 20M input, 5M output tokens | $45.00 | $37.50 | Grok 4.20 Reasoning, $7.50 less |
| Scale: 500M input, 100M output tokens | $1,000 | $875.00 | Grok 4.20 Reasoning, $125.00 less |
Standard rates, without caching or batch discounts. Volumes are per month.
Specifications side by side
| GPT-6.1 Terra | Grok 4.20 Reasoning | |
|---|---|---|
| Provider | OpenAI | xAI |
| Category | Language models | Language models |
| Status | Generally available | Generally available |
| Headline price | $2.00 / 1M tokens | $1.56 / 1M tokens |
| Input | $1.00 / 1M tokens | $1.25 / 1M tokens |
| Output | $5.00 / 1M tokens | $2.50 / 1M tokens |
| Cached input | $0.05 / 1M tokens | $0.20 / 1M tokens |
| Context window | 1.05M | 1M |
| Max output | 128k | No data |
| Released | Oct 26, 2026 | March 2026 |
| Knowledge cutoff | No data | No data |
| Licence | Proprietary | Proprietary |
| Capabilities | Vision, Reasoning, Tool calling, Structured output, Prompt caching | Vision, Reasoning, Tool calling, Structured output, Prompt caching, Batch API |
| API model id | gpt-6.1-terra | grok-4.20-0309-reasoning |
Frequently asked questions
Should I choose GPT-6.1 Terra or Grok 4.20 Reasoning?
Choose GPT-6.1 Terra for reused prompts and documents (RAG, agents) and the latest release. Choose Grok 4.20 Reasoning for high-volume, cost-sensitive work and writing and code generation.
Which is cheaper, GPT-6.1 Terra or Grok 4.20 Reasoning?
Grok 4.20 Reasoning is 22% cheaper than GPT-6.1 Terra at the headline price ($1.56 / 1M tokens vs $2.00 / 1M tokens).
Which has the larger context window, GPT-6.1 Terra or Grok 4.20 Reasoning?
GPT-6.1 Terra reads more per request: 1.05M tokens against 1M.
What is the difference between GPT-6.1 Terra and Grok 4.20 Reasoning?
GPT-6.1 Terra is made by OpenAI and Grok 4.20 Reasoning by xAI. Grok 4.20 Reasoning is 22% cheaper than GPT-6.1 Terra at the headline price ($1.56 / 1M tokens vs $2.00 / 1M tokens). GPT-6.1 Terra reads more per request: 1.05M tokens against 1M. GPT-6.1 Terra is the newer model (Oct 26, 2026, against March 2026). Only Grok 4.20 Reasoning offers batch api.
How much do GPT-6.1 Terra and Grok 4.20 Reasoning cost per month?
At 20 million input and 5 million output tokens a month, GPT-6.1 Terra costs $45.00 and Grok 4.20 Reasoning costs $37.50, at standard rates.
Which is newer, GPT-6.1 Terra or Grok 4.20 Reasoning?
GPT-6.1 Terra was released on Oct 26, 2026 and Grok 4.20 Reasoning on March 2026.