Is GPT-5 mini cheaper than GPT-5.5 Pro?

Yes — GPT-5 mini is dramatically cheaper. GPT-5 mini costs $0.25/M input and $2/M output, while GPT-5.5 Pro costs $30/M input and $180/M output. That's 99.2% cheaper on input and 98.9% cheaper on output.

Which is better for coding — GPT-5 mini or GPT-5.5 Pro?

GPT-5.5 Pro delivers superior chain-of-thought reasoning for complex coding tasks, but GPT-5 mini handles most code assistance at 99% lower cost. Unless you need the absolute best multi-step reasoning, GPT-5 mini is the better value.

How much would I save using GPT-5 mini instead of GPT-5.5 Pro?

For a workload of 1M input + 500K output tokens/month, GPT-5 mini costs $1.25/month vs GPT-5.5 Pro's $120/month — saving $118.75/month (99%). At scale (10M input + 5M output), you save $1,187.50/month.

When should I choose GPT-5.5 Pro over GPT-5 mini?

Choose GPT-5.5 Pro when: (1) you need the absolute best chain-of-thought reasoning, (2) cost is not a concern, (3) you need the 1.05M context window for very long documents. For everything else, GPT-5 mini delivers excellent quality at 99% lower cost.