Short answer: neither is always cheaper. 
Claude usually wins for large, stable prefixes reused many times within its TTL; OpenAI is often cheaper for low or unpredictable reuse—and is generally simpler because caching is automatic.
Typical pricing mechanics
|
 Claude |
OpenAI |
| Cache write |
Usually a premium: about 1.25× input price for 5 minutes or 2× for 1 hour |
Usually billed at normal input price |
| Cache read |
Commonly about 0.1× normal input price |
Model-dependent: commonly around 0.5×, while some newer models may offer discounts closer to 0.1× |
| Control |
Explicit cache breakpoints/TTL, with some automatic options |
Automatic prefix matching |
| Main limitation |
Write premium and TTL expiry |
Exact prefix matching and model-specific cache rates |
Because OpenAI’s cached-input rate varies by model and pricing revision, the answer can change substantially depending on the exact models being compared.
Break-even intuition
Assume the repeated prefix would cost 1 unit uncached:
- Claude, 5-minute cache: approximately
1.25 + 0.1 × (N − 1)
- Claude, 1-hour cache: approximately
2 + 0.1 × (N − 1)
- OpenAI at a 50% cached-input rate: approximately
1 + 0.5 × (N − 1)
Under those assumptions:
- Claude’s 5-minute cache generally beats uncached requests after about two total uses.
- Claude’s 1-hour cache generally needs about three uses.
- Compared directly with OpenAI at a 50% cached rate, Claude’s 5-minute option usually wins from roughly the second use, and the 1-hour option after roughly four uses.
However, if the relevant OpenAI model charges only about 10% for cached input, OpenAI may match or beat Claude because it has no cache-write premium.
Practical verdict
Choose Claude caching when:
- You reuse a large system prompt, document set, codebase, tool schema, or conversation context repeatedly.
- Several requests arrive within the same 5-minute or 1-hour window.
- You can keep the cached prefix stable.
- The Claude model’s ordinary input price is comparable to the OpenAI model’s.
Choose OpenAI caching when:
- Reuse is sporadic or often limited to one hit.
- Prompts change frequently.
- You prefer zero configuration and automatic prefix caching.
- The specific OpenAI model has a very low cached-input rate or a substantially lower base input price.
Remember that only the cached prefix benefits. Dynamic content inserted before the stable context—timestamps, request IDs, changing tool definitions, or user-specific instructions—can prevent a cache hit. Output-token costs are unaffected.
Bottom line: for high-reuse, long-context workloads, Claude is often cheaper—sometimes considerably so. For low-reuse workloads, or when using an OpenAI model with approximately 10% cached-input pricing, OpenAI may be cheaper. Compare the exact model prices, cache TTL, hit rate, and prefix size rather than comparing providers in the abstract.
