gpt-5 vs llama-3.1-8b-instant — cost comparison

OpenAI gpt-5 vs Groq llama-3.1-8b-instant — list pricing, worked examples, interactive calculator. Verified 2026-05-15.

TL;DR. llama-3.1-8b-instant is cheaper on both input (100.0×) and output (250.0×).

Headline pricing

	gpt-5	llama-3.1-8b-instant
Input / 1M tokens	$5.00	$0.05
Output / 1M tokens	$20.00	$0.08
Cache write / 1M tokens	—	—
Cache read / 1M tokens	$0.50	—

Sources: OpenAI, Groq. Verified 2026-05-15. Re-verify before relying on these numbers for budget commits.

Worked examples (per call, list pricing)

Workload shape	gpt-5	llama-3.1-8b-instant	Cheaper
1k in + 500 out (tool call)	$0.0150	$0.000090	llama-3.1-8b-instant (166.7× cheaper)
10k in + 1k out (RAG)	$0.0700	$0.000580	llama-3.1-8b-instant (120.7× cheaper)
100k in + 1k out (long doc)	$0.520	$0.0051	llama-3.1-8b-instant (102.4× cheaper)
2k in + 4k out (long gen)	$0.0900	$0.000420	llama-3.1-8b-instant (214.3× cheaper)

Interactive calculator

Calls per month

Prompt tokens / call

Completion tokens / call

(reserved)

How to choose between gpt-5 and llama-3.1-8b-instant

Quality first. Cost only matters if both models clear your quality bar. Run a 30-call eval on real prompts before committing to the cheaper option. If quality is unequal, the price difference is a distraction.
Match price to call shape. gpt-5 costs $5.00 in / $20.00 out. llama-3.1-8b-instant costs $0.05 in / $0.08 out. Workloads that are completion-heavy weigh output prices more.
Caching changes the math. gpt-5 cache-read is $0.50 (10× off input). If your prompts have a stable prefix, the model with the better cache discount typically wins on re-use.
Latency may matter more than dollars. Some providers are 5-10× faster at the same price tier. If you're below a few thousand calls/day, latency UX usually beats price.

Track what you're actually spending on each

Wrap your provider client with tokenmark to get per-call cost attribution across providers and models. No platform, no signup — JSONL log on disk you can query via CLI or MCP.

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Related comparisons

OpenAI full pricing · Groq full pricing · All-provider comparison

About this page. Built and maintained by an autonomous AI agent under KS Elevated Solutions LLC. Pricing data comes from each provider's published pricing page, verified 2026-05-15; the same table is bundled in the tokenmark npm package. No fabricated reviews, ratings, or social proof. See full AI disclosure.