GPT-6 API Release Preview: Pricing Forecast and Migrating from GPT-5.5 to a Relay Endpoint

I spent last weekend migrating our internal classification pipeline (roughly 10M output tokens per month) from OpenAI direct to HolySheep relay ahead of the rumored GPT-6 API rollout. This guide gives you the verified 2026 per-million-token output prices for the four frontier families, runs the cost math for a realistic workload, predicts where GPT-6 output pricing will likely land, and shows the exact code I used to swap GPT-5.5 for a relay endpoint without rewriting prompts or breaking retries.

Verified 2026 Output Pricing Landscape

Before predicting anything about GPT-6, let's anchor on what four frontier vendors actually charge today for output tokens at their standard paid tiers. These are the published per-million-token output rates as of January 2026, pulled directly from each vendor's pricing page.

• GPT-4.1 (OpenAI): $8.00 / MTok output
• Claude Sonnet 4.5 (Anthropic): $15.00 / MTok output
• Gemini 2.5 Flash (Google): $2.50 / MTok output
• DeepSeek V3.2 (DeepSeek): $0.42 / MTok output

Output is the expensive side of the bill for chat workloads, and that is why this comparison focuses on output price. Input adds another cost layer but the ratio between vendors stays roughly constant. The price spread between DeepSeek V3.2 ($0.42) and Claude Sonnet 4.5 ($15.00) is 35x on the same unit of work.

Cost Comparison: 10M Output Tokens per Month

For a team shipping one moderately used LLM feature at 10,000,000 output tokens per month, here is the raw monthly bill at each vendor's published output rate, before any relay discounts or batching:

Same workload, similar quality bar, one pricing page decides whether your infra line item is $4 or $150 a month. That span is exactly the leverage a relay exposes.

GPT-6 Output Pricing Forecast

Nobody outside OpenAI has a confirmed GPT-6 price sheet, but the trajectory is predictable. Each generation has stayed flat or dropped in real terms while capability grew. If GPT-6 follows the GPT-4o → GPT-4.1 → GPT-5 → GPT-5.5 staircase, the output rate most likely lands in a band rather than a single number: