GPT-4o vs Claude Sonnet 4.5: optimized frontier API rates compared
GPT-4o is cheaper for low-cache workloads and output-heavy requests. Claude Sonnet 4.5 becomes cheaper when prompt caching is highly active.
Optimized premium intelligence confrontation.
GPT-4o and Claude Sonnet 4.5 represent premium, highly optimized intelligence. Their cost efficiency depends on how your app structures requests.
By TechCompare · Updated
Cost Comparison
Based on 100,000 input tokens (50% cached), 5,000 output tokens, and 100 requests.Prices are fetched live from OpenRouter and may include temporary promotional discounts not accounted for in our article and comparison figures.
Side-by-side specs
| Spec | GPT-4o | Claude Sonnet 4.5 |
|---|---|---|
| Input Cost (per M) | $2.50 (better on this spec) | $3.00 |
| Output Cost (per M) | $10.00 (better on this spec) | $15.00 |
| Cached Input (per M) | $1.25 | $0.30 (better on this spec) |
| Batch Discount | 50% | 50% |
How they differ
GPT-4o costs $2.50 per million input tokens and $10.00 per million output tokens, with a 50% caching discount. Claude Sonnet 4.5 costs $3.00 per million input tokens and $15.00 per million output tokens, with a 90% caching discount.
Verdict
GPT-4o wins the base rows: $2.50/M input against $3.00 and $10.00/M output against $15.00. Sonnet 4.5's lever is its 90% cache discount versus GPT-4o's 50%, dropping cached input to $0.30/M versus $1.25/M. The crossover sits near 50% prompt reuse. Below it, GPT-4o's lower bases hold. Above it, Sonnet's deeper cache overtakes. Batch ties at 50% on both, so it doesn't tilt the live-call math.
Which should you pick?
Choose GPT-4o
Standard low-cache requests, transactional text chat, and output-heavy tasks.
Choose Claude Sonnet 4.5
Document summarization, high-caching multi-turn chats, and agent frameworks.