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RAGLong Context vs RAG: Which Is Cheaper?
Million-token context windows make it tempting to send everything. But you pay for every token on every call, and some models charge more above a threshold.
RAG is usually cheaper per call; long context can win when the same large context is reused and cached, or when retrieval quality is poor.
The math
Cost per call is roughly context tokens times input price plus output tokens times output price. Sending 200,000 tokens of context on every call costs 50 times more input than sending 4,000 retrieved tokens.
Price tiers matter
Some models charge more for long prompts: Claude Haiku 5.5 rises from $0.10 to $0.50 per 1M input tokens above 100,000 tokens, and Gemini 3.1 Pro from $2 to $4 above 200,000.
When long context wins
- The same document set is reused across many calls, so it can be cached.
- Answers need reasoning across the whole document.
- Retrieval keeps missing the right passage.
When RAG wins
- Large or changing knowledge bases.
- Many users asking different questions.
- Cost-sensitive, high-volume traffic.
Estimate yours with the RAG cost calculator.
Frequently asked questions
Is RAG cheaper than long context?
Usually per call, because you send far fewer tokens. Long context can compete when the context is reused and cached.
Do long prompts cost more per token?
On some models. Claude Haiku 5.5 and Gemini 3.1 Pro charge more above 100K and 200K tokens respectively.
Sources: Anthropic's pricing page, Google's Gemini API pricing page. Checked October 30, 2026.
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