USE CASE · VERIFIED 1 NOV 2026
What's the cheapest AI API for RAG pipelines right now?
For a typical RAG workload of 400M input tokens and 40M output tokens a month, DeepSeek V4.1 Flash is cheapest at $38/mo, followed by GPT-6 Luna and Claude Haiku 5.5, which tie at $60/mo. Qwen3.8 Flash follows at $79/mo and GLM 5.3 Flash at $80/mo.
Worked example: 400M input, 40M output tokens/month
Retrieved chunks stuffed into the prompt, short grounded answers. The six cheapest of the 35 models we track, plus two flagships for scale. Open-weight models are priced at the original provider's own list price.
Why RAG pricing is input-heavy
RAG pipelines stuff retrieved chunks into the prompt and then ask for a short grounded answer, so the token ratio is almost always input-heavy — in this worked example, 10 input tokens for every output token. That means the per-token input price matters far more than the output price for total cost. Models with a cheap input rate but expensive output (like Gemini 2.5 Flash at $0.3/$2.5) can end up costing more than models with a slightly higher input rate but much cheaper output (like DeepSeek V3 at $0.27/$0.41), depending on your actual ratio. Always re-run the math on your own input/output split before picking a model on price alone.
Budget tier is where RAG actually lives
Every model worth considering for a cost-sensitive RAG pipeline sits in the budget tier: DeepSeek V4.1 Flash, GPT-6 Luna, Claude Haiku 5.5, Qwen3.8 Flash, GLM 5.3 Flash, GPT-4o mini, MiniMax M3.1 Flash, DeepSeek V3, MiniMax M3, MiMo V2.6 Pro, and Gemini 2.5 Flash all land between $38 and $220/mo for this workload. Mid-tier models like Gemini 3 Flash ($320/mo) or GPT-6.1 Terra ($600/mo) cost multiples more for the same volume. Unless your RAG answers need deeper reasoning over the retrieved context, there's rarely a reason to leave the budget tier for straightforward grounded Q&A.
Context window, caching, and batching change the math
Most budget models here offer a 1M token context window, which comfortably fits large chunk sets — GPT-4o mini and DeepSeek V3 are outliers at 128K, worth checking if your retrieved context plus history is large. Prompt caching is particularly relevant for RAG because the same chunks, system prompt, or few-shot examples often repeat across requests; providers that support caching typically discount repeated input tokens, often around half, which can meaningfully cut your effective cost below the sticker price used here. Batching output generation (processing many queries asynchronously) can also unlock lower rates on some providers. Check your specific provider's caching and batching terms — the numbers above assume no discounts.
How we'd actually decide
- Situation: Lowest possible bill, no special quality needs — DeepSeek V4.1 Flash — cheapest at $38/mo for this workload
- Situation: Want a non-DeepSeek budget option with similar cost — GPT-6 Luna or Claude Haiku 5.5 — both land at $60/mo
- Situation: Need output-heavy answers (longer grounded responses) — DeepSeek V3 — cheapest output rate at $0.41/1M among budget models
- Situation: Context exceeds 128K and you need headroom — DeepSeek V4.1 Flash or MiMo V2.6 Pro — both offer 1M context at budget pricing
Worked example uses standard (non-batch, non-cached) list pricing verified 1 November 2026. Prices change; use the calculator for today's numbers with your own volume. DeepSeek figures use DeepSeek's own weekday list price. On the weekends of 3–4 and 10–11 October we saw DeepSeek charge half of that, so if your jobs run on weekends the DeepSeek numbers can come in lower.