Anthropic didn't launch a cheaper model. Its $3 Sonnet just made the $5 Opus optional.
On June 30, Anthropic shipped Claude Sonnet 5.
The internet filed it under "cheaper agent model."
That framing is the misdirection.
Sonnet 5 ties Opus 4.8 on knowledge work, 1,618 to 1,615 at 40% less