If you're choosing between OpenAI's GPT-4o and Anthropic's Claude Sonnet 4 for a production API integration, pricing will be one of your top three decision factors. This comparison gives you real numbers — no marketing fluff.
Current Pricing (May 2026)
| GPT-4o | Claude Sonnet 4 | |
|---|---|---|
| Input tokens | $2.50 / 1M | $3.00 / 1M |
| Output tokens | $10.00 / 1M | $15.00 / 1M |
| Context window | 128K tokens | 200K tokens |
| Prompt caching (input) | $1.25 / 1M (50% off) | $0.30 / 1M (90% off) |
| Batch API discount | 50% off | 50% off |
Claude Sonnet 4 costs 20% more on input tokens, and 50% more on output tokens versus GPT-4o. But the picture changes significantly when you factor in prompt caching.
Real Cost Examples
Use Case 1: Customer Support Chatbot
1,000 users × 10 messages/day × 30 days = 300,000 API calls/month Avg: 500 input tokens + 300 output tokens per call
| GPT-4o | Claude Sonnet 4 | |
|---|---|---|
| Monthly cost | $1,050 | $1,500 |
| With prompt caching (1,500 token system prompt) | $600 | $285 |
Claude wins decisively once prompt caching is factored in. Anthropic's 90% cache discount vs OpenAI's 50% makes a material difference when your system prompt is long.
Use Case 2: RAG Pipeline
10,000 requests/day × 3,000 input tokens (document chunks) × 500 output tokens
| GPT-4o | Claude Sonnet 4 | |
|---|---|---|
| Monthly cost | $23,250 | $29,700 |
| Cost per query | $0.078 | $0.099 |
GPT-4o wins on raw price for RAG workloads where the context isn't cacheable (each query has unique retrieved documents).
Use Case 3: AI Agent (multi-step)
50 agent runs/day × 8 steps × 1,500 tokens/step
| GPT-4o | Claude Sonnet 4 | |
|---|---|---|
| Monthly cost | $675 | $810 |
| With caching (static system + tools schema) | $400 | $250 |
Claude's extended 1-hour cache TTL (vs OpenAI's 5-minute default) is a significant advantage for long-running agent sessions.
Which Should You Choose?
Choose GPT-4o when:
- Your prompts are mostly dynamic (RAG, per-user context, real-time data)
- You need the cheapest absolute per-token rate
- Your team is already on the OpenAI ecosystem (Assistants, Fine-tuning)
Choose Claude Sonnet 4 when:
- You have a large, static system prompt (1,000+ tokens)
- You're building long-context applications (Claude's 200K window vs GPT-4o's 128K)
- You're running agent workflows where the tools schema is stable
The Caching Factor is Decisive
The single biggest variable in this comparison is prompt caching. If your system prompt is 2,000 tokens and you serve 100,000 requests/month:
- Without caching: Claude costs ~$6,000/month vs GPT-4o's ~$5,000/month
- With caching: Claude costs ~$1,200/month vs GPT-4o's ~$3,000/month
The decision reverses entirely. Run the numbers for your specific prompt length and volume using the calculator below.
Bottom Line
Neither model dominates across all workloads. GPT-4o is cheaper for high-churn contexts; Claude Sonnet 4 is dramatically cheaper when caching applies. Build your cost model around your actual system prompt length, not just per-token rates.