Simon Willison on AI

Simon Willison@simonw

This is notable: Opus 4.5 is ~60% more expensive than Sonnet ($25/million output compared to $15/million) but if it can use 76% fewer output reasoning tokens for the same complex task it may end up cheaper!

1.1K likes43 repliesPosted Nov 24, 2025

Remix this post

Your note

Private to you, and used when you remix this post.

Viral score

Based on absolute engagement — the platform doesn’t expose follower counts here, so large accounts score higher.

From likes, comments.

Why it worked

Opens with a short, self-contained line that is easy to take in at a glance.
Uses concrete numbers instead of vague claims, which makes it credible and quotable.
The opening line stands alone, so it reads completely before the post is expanded.
Short enough to read in full without expanding, which removes a step before the point lands.

The mechanics

Hook: Plain observation
Structure: Hook
Style: Conversational paragraphs at a steady pace.
Tone: energetic
Mechanisms: Specificity
Written for: People building with AI

Analysis by ViralLoop — not written by the original author.

Post by Simon Willison on X