o3-pro vs GPT-5 Pro: cost compared
Last verified
GPT-5 Pro is 25% cheaper on input and -50% cheaper on output than o3-pro. Whether that makes it the right choice depends entirely on whether it does your task well enough — this page gives you the cost side of that trade, precisely.
Rates side by side
| $ per million tokens | o3-pro | GPT-5 Pro |
|---|---|---|
| Input | $20.00 | $15.00 |
| Output | $80.00 | $120.00 |
| Cached input | — | — |
| Output : input ratio | 4.0× | 8.0× |
What the difference is worth
Monthly cost for the same workload on each, without caching:
| Workload | o3-pro | GPT-5 Pro | Difference |
|---|---|---|---|
| Support chatbot 1,000 conversations/month · 2,000 in + 500 out each | $80.00 | $90.00 | $-10.0000 saved |
| RAG search 10,000 queries/month · 8,000 in + 400 out each | $1920 | $1680 | $240 saved |
| Bulk extraction 10,000 documents · 3,000 in + 300 out each | $840 | $810 | $30.00 saved |
| Coding agent 100 runs/month · 400,000 in + 20,000 out each | $960 | $840 | $120 saved |
Which to use
GPT-5 Pro if the task is well-specified and mechanical — extraction, classification, formatting, routine transformation. The saving is real and compounds with volume.
o3-pro if the task involves genuine reasoning, long-horizon planning, or work where a wrong answer is expensive to catch. Paying 1.3× more on input is trivial compared to the cost of shipping a bad result.
Both are OpenAI models, so switching is usually a one-line change and the tokenizer is the same — which makes this a genuinely easy experiment to run. Test on your own workload before deciding.
Don't skip caching
Where prompt caching is available, it frequently matters more than the choice between these two.
Sources
OpenAI rates verified 2026-08-05 (source). OpenAI rates verified 2026-08-05 (source).