Originally published at API Cost Lab .

Last updated: October 2026

"What's the cheapest LLM API?" is the wrong question — or rather, it's a question with a trap in it. The model with the lowest per-token price is rarely the cheapest one on your invoice. Your real bill is decided by three things the headline price doesn't show: cache rates, output ratios, and pricing thresholds.

Here's the honest comparison, using only verified current prices.

The Verified Price Table

These are the models with confirmed pricing as of October 2026. No rumors, no "reportedly" — just published rate cards:

Model Input / 1M Cached input / 1M Output / 1M

GPT-5.6 Sol (promo) $4.00 $0.40 $20.00

GPT-6.1 Sol $2.00 $0.10 $10.00

Claude Opus 5.5 $4.00 $0.20 $20.00

Claude Sonnet 5 $2.00 — $10.00

Gemini 4 Argon (intro) $2.00 — $10.00

Gemini 4 Argon (from Dec 1) $4.00 — $20.00

Muse Wonder $4.00 — $20.00

Two deadlines matter here.…