Updated June 2026. We ran both flagships side by side for a full billing cycle on four real apps — here's what each cost, where quality differed, and which to pick.
On paper these two flagships look almost identical: GPT-5.5 at $5 / $30 per million tokens and Claude Opus 4.8 at $5 / $25. Same input rate, and Claude is $5 cheaper on output. But headline rates rarely predict the real bill — tokenization, output length and caching all move the number. We ran both models on four production applications for a full billing cycle with identical prompts and matched traffic. Here's what actually happened. To price your own workload, use the live comparison.
| GPT-5.5 | Claude Opus 4.8 | |
|---|---|---|
| Input / million | $5.00 | $5.00 |
| Output / million | $30.00 | $25.00 |
| Context window | 1.05M | 1M |
On output rate alone, Claude is ~17% cheaper. Because output is the expensive direction (5×+ input), that gap widens on any output-heavy workload.
Across four apps — a customer-support agent, a code-review bot, a contract-analysis pipeline, and a content-generation tool — with identical prompts and matched user traffic:
That's ~13% less on Claude over the cycle, driven almost entirely by the lower output rate and slightly tighter tokenization on English prose.
The spread was not uniform. On the two output-heavy apps (content generation, code review), Claude's advantage was largest — the $25 vs $30 output gap compounds with every generated token. On the input-heavy contract-analysis pipeline, the two were nearly tied, because the input rate is identical and output is short.
The lesson generalizes: the bigger your output-to-input ratio, the more Claude Opus 4.8 saves. If your workload is mostly reading (long input, short output), the two flagships cost about the same and you should choose on quality, not price.
Per-call quality scores were statistically indistinguishable on three of the four apps. Claude won narrowly on contract analysis (long-context comprehension). For most teams, this means the decision is economic: same quality, Claude is ~13% cheaper at the flagship tier.
max_tokens is the easiest win.Yes — same $5 input rate, but $25 vs $30 output. Over a 30-day, four-app test the totals were $3,650 (Claude) vs $4,200 (GPT-5.5), about 13% less on Claude.
In our test, per-call quality was statistically tied on three of four apps, with Claude slightly ahead on long-context contract analysis. For most workloads quality is a wash, so price decides.
Use the side-by-side calculator — it runs the same prompt across both and shows the real difference.
Prices synced from each vendor's official pricing page, June 2026.