Why I Switched from GPT-6 Astra to Opus 5.5

3-Line TL;DR

I moved from Astra to Opus 5.5 because the output is better and the tokens are 60% cheaper
In a same-prompt test of two games, Opus won both rounds, but the bills split one each
Hand visible, finished work to Opus, but judge it by what each task actually cost

When Astra launched, my first thought was that Fable should get nervous
Since Opus 5.5 arrived, my pick for both value and output has moved to Opus
In my use, Opus 5.5 also feels roomier on usage
That is a felt impression from daily use, not a measured limit or a controlled test
Turns out the one that needed to get nervous was Astra, not Fable

Moe Lueker gave both models the same prompt for two games and allowed no fixes (Moe Lueker, September 25)
Both started in an empty folder, Astra in Codex and Opus in Claude Code
Round 1 was a runner, and Round 2 was a cozy island builder

Round 2 island builders from one prompt, with GPT-6 Astra's Tiny Tides next to Claude Opus 5.5's larger, busier island

Source: Moe Lueker — Claude Opus 5.5 vs GPT-6 Astra: Same Prompt, Two Games, Real Cost

In the runner, Opus added diving, braking, sprinting, checkpoints and background music
Nobody asked for any of it
Astra's runner had real art and a parallax background, the best GPT-6 build by the tester's account
Opus wrote 2,405 lines of game code, and Astra wrote 358
On the island, Opus grew the land as you built, added a night mode and rewarded houses next to paths
Astra's island had more tree and house types, and that was about it
One tester ran each model once per round, so treat it as a case, not a benchmark

Model	Input per 1M tokens	Output per 1M tokens
GPT-6 Astra	$10	$50
Claude Opus 5.5	$4	$20

Standard API rates, Astra short-context tier, checked September 28, 2026: OpenAI pricing, Anthropic

Opus lists 60% lower than Astra on both input and output
Anthropic says Opus 5.5 at medium effort scored 54.6% on FrontierCode, above Astra's best 53.3%, at about a fifth of the cost per task
Anthropic graded and published that report card itself, so read the settings too
The same page puts Astra ahead on AutomationBench, 41.4% to 40.0%
Credit where due, it published the loss on its own launch page

Build-turn API cost from the same prompt: Opus 5.5 $15.25 vs Astra $7.09 on the runner, and $5.40 vs $6.88 on the island builder

Data: Moe Lueker, build turn only at list API rates — chart by HSL

On the runner, Opus wrote 256K output tokens to Astra's 36K, and the bill was $15.25 against $7.09
A 60% discount does not survive seven times the work
On the island builder, the bill flipped to $5.40 for Opus and $6.88 for Astra
Across both games, Opus cost $20.65 and Astra $13.97, about $7 more for two better games
The unrequested background music was billed down to the last token

Job	Start with	Why
Front end, design, games	Opus 5.5	Better result in both same-prompt rounds
Long back-end debugging	Compare with Astra	The same tester keeps Astra for back end, and one Reddit report below agrees
Fixed budget	Set a cap first	Opus may build more than you asked for

An r/codex author found Opus productive but rated Astra and Fable higher for deep async-runtime design, a real counterexample to "Opus wins everything" (Reddit)
Another commenter in the same thread said Opus fixed a bot that Astra failed to fix after using a lot of quota, which is one person's experience rather than a measured bill (Reddit)

Q. Is Opus 5.5 always cheaper than Astra?
- Per token yes, but per task it depends on how excited Opus gets about the job
Q. Does one same-prompt test prove Opus is better?
- No, one tester ran each model once per round, so repeat it on your own work
Q. Can I rerun the exact test?
- The prompt is not published, so match the empty folders and effort settings and use your own prompt
Q. Should I drop Astra entirely?
- Not if you do long back-end debugging, where both the tester and a Reddit report still reach for it