Claude Sonnet 5's promo price will revert to the standard list price after August 31 — resolves 2026-09-01

The debate: Anthropic put a limited-time promotional price on the Claude Sonnet 5 API that expires on 2026-08-31, and people were guessing whether it would be extended.

Why it matters: for heavy users, a twofold difference in unit price means the margin model of the whole product has to be redone.

Who is on each side: the pricing-power camp thinks frontier models still hold their price and the promotion is only short-term customer acquisition; the competition camp thinks competition has already forced the big labs into lasting price cuts.

Our call: once the promotion ends on September 1, the official pricing page will return to the pre-promotion standard list price of $3 per million input tokens and $15 per million output tokens, against the promotional $2 and $10. Our confidence is 85%, the highest of the calls we logged on 2026-07-31.

SemiAnalysis
“Anthropic's ARR has exploded from $9B to over $44B…”

SemiAnalysis
“AWS margins inflected this past quarter driven…”

Check Anthropic's official API pricing page on 2026-09-01: a list price equal to the standard $3/$15 is a hit; still promotional, or an announced extension or some other new price, is a miss.

Miss (settled 2026-09-30)

The prediction: after the promotional price for Anthropic's Claude Sonnet 5 model expired on August 31, the official price would go back to the standard price on September 1. How it would be checked, decided when the prediction was made: look at Anthropic's official pricing page on September 1. Back at the standard price means the prediction was right; still at the promotional price, an extended promotion, or any other new price means it was wrong. On 2026-09-30 the official pricing page said the promotional price ($2 per million input tokens and $10 per million output tokens) had become the standard price, and that the increase to $3 and $15 planned for September 1 would not happen. The price did not go back up, so the prediction was wrong. The check was due on September 1, a date set when the prediction was made, and came 29 days late.

Evidence used to settle it

platform.claude.com · checked 2026-09-30
“The $2/$10 per million input/output token pricing for Claude Sonnet 5, announced at launch as introductory pricing through August 31, 2026, is now the standard price. The previously scheduled increase to $3/$15 … on September 1, 2026 will not occur.”