High-volume, cost-sensitive work
Choose Claude Mythos 5.1
Claude Mythos 5.1 costs 70% less on a typical mix of three input tokens for every output token ($20.00 against $67.50 per million tokens).
Claude Mythos 5.1 vs GPT-5.4 Pro: price, context and capabilities
Choose Claude Mythos 5.1 for high-volume, cost-sensitive work, writing and code generation and the latest release; on the other points the two are level or the data is missing.
In short
- Claude Mythos 5.1 is 70% cheaper than GPT-5.4 Pro at the headline price ($20.00 / 1M tokens vs $67.50 / 1M tokens).
- GPT-5.4 Pro reads more per request: 1.05M tokens against 1M.
- Claude Mythos 5.1 is the newer model (September 2026, against Mar 5, 2026).
- Only Claude Mythos 5.1 offers prompt caching.
Which should you choose?
Each answer below comes straight from the published prices, specifications and independent benchmark results.
Writing and code generation
Choose Claude Mythos 5.1
Claude Mythos 5.1 charges $50.00 per million output tokens, against $180.00 for GPT-5.4 Pro. Output dominates the bill when answers are long.
Latest release
Choose Claude Mythos 5.1
Claude Mythos 5.1 is the newer release (September 2026, against Mar 5, 2026 for GPT-5.4 Pro).
Monthly cost at three volumes
| Volume | Claude Mythos 5.1 | GPT-5.4 Pro | Difference |
|---|---|---|---|
| Prototype: 1M input, 250K output tokens | $22.50 | $75.00 | Claude Mythos 5.1, $52.50 less |
| Production: 20M input, 5M output tokens | $450.00 | $1,500 | Claude Mythos 5.1, $1,050 less |
| Scale: 500M input, 100M output tokens | $10,000 | $33,000 | Claude Mythos 5.1, $23,000 less |
Standard rates, without caching or batch discounts. Volumes are per month.
Specifications side by side
| Claude Mythos 5.1 | GPT-5.4 Pro | |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Category | Language models | Language models |
| Status | Generally available · Limited access | Legacy |
| Headline price | $20.00 / 1M tokens | $67.50 / 1M tokens |
| Input | $10.00 / 1M tokens | $30.00 / 1M tokens |
| Output | $50.00 / 1M tokens | $180 / 1M tokens |
| Cached input | $0.25 / 1M tokens | No data |
| Context window | 1M | 1.05M |
| Max output | 128k | 128k |
| Released | September 2026 | Mar 5, 2026 |
| Knowledge cutoff | No data | August 2025 |
| Licence | Proprietary | Proprietary |
| Capabilities | Vision, Reasoning, Tool calling, Structured output, Prompt caching, Batch API | Vision, Reasoning, Tool calling, Structured output, Batch API |
| API model id | claude-mythos-5-1 | gpt-5.4-pro |
Frequently asked questions
Should I choose Claude Mythos 5.1 or GPT-5.4 Pro?
Choose Claude Mythos 5.1 for high-volume, cost-sensitive work, writing and code generation and the latest release; on the other points the two are level or the data is missing.
Which is cheaper, Claude Mythos 5.1 or GPT-5.4 Pro?
Claude Mythos 5.1 is 70% cheaper than GPT-5.4 Pro at the headline price ($20.00 / 1M tokens vs $67.50 / 1M tokens).
Which has the larger context window, Claude Mythos 5.1 or GPT-5.4 Pro?
GPT-5.4 Pro reads more per request: 1.05M tokens against 1M.
What is the difference between Claude Mythos 5.1 and GPT-5.4 Pro?
Claude Mythos 5.1 is made by Anthropic and GPT-5.4 Pro by OpenAI. Claude Mythos 5.1 is 70% cheaper than GPT-5.4 Pro at the headline price ($20.00 / 1M tokens vs $67.50 / 1M tokens). GPT-5.4 Pro reads more per request: 1.05M tokens against 1M. Claude Mythos 5.1 is the newer model (September 2026, against Mar 5, 2026). Only Claude Mythos 5.1 offers prompt caching.
How much do Claude Mythos 5.1 and GPT-5.4 Pro cost per month?
At 20 million input and 5 million output tokens a month, Claude Mythos 5.1 costs $450.00 and GPT-5.4 Pro costs $1,500, at standard rates.
Which is newer, Claude Mythos 5.1 or GPT-5.4 Pro?
Claude Mythos 5.1 was released on September 2026 and GPT-5.4 Pro on Mar 5, 2026.