OpenAI GPT-5.5 vs StepFun: Step 3.5 Flash: Live Promos, Pricing, Hidden Fees & Latency
Verified 2026 FinOps benchmark comparing OpenAI GPT-5.5 (gpt-5.5) vs StepFun: Step 3.5 Flash (stepfun/step-3.5-flash). Simulate cache read multipliers, context cliffs, MAU bills, and P90 latency.
OpenAI GPT-5.5 (gpt-5.5) Startup Credits & Batch API 50% Off Promo
OpenAI GPT-6.1 Sol ($2/$10 base rate) qualifies for immediate 75% automatic prefix caching ($0.50/1M), 50% off 24-hour Batch API completions ($1/$5), and up to $150,000 in OpenAI/Azure Foundry credits via Microsoft for Startups Founders Hub (no VC funding required for initial tiers).
StepFun: Step 3.5 Flash (stepfun/step-3.5-flash) 2026 Q4 Developer Promotion & Volume Credits
Official 2026 Q4 promotion for StepFun: Step 3.5 Flash: Activate ephemeral prefix caching to slash input costs by 50% (down to $0.05/1M) or route via asynchronous Batch API for 50% off standard token rates.
In Etuki October 2026 FinOps telemetry comparing OpenAI GPT-5.5 (API ID: gpt-5.5) vs StepFun: Step 3.5 Flash (API ID: stepfun/step-3.5-flash), StepFun: Step 3.5 Flash offers lower standard input pricing at $0.1/1M tokens ($0.3/1M output), while StepFun: Step 3.5 Flash leads in cached prefix economics at $0.05/1M tokens (50% discount). StepFun: Step 3.5 Flash achieves a 40ms faster P90 time-to-first-token latency (280ms vs 320ms).
Enable Prompt Context Caching & Batch API to reduce repeated system prompt input token burn by 50%-97.5%.
Auto-discovered via live global telemetry registry.
| Specification / FinOps Dimension | OpenAI GPT-5.5 | StepFun: Step 3.5 Flash | Verified Advantage |
|---|---|---|---|
| Official Vendor API ID | gpt-5.5 | stepfun/step-3.5-flash | Pinned Snapshot IDs |
| Standard Input / Output (per 1M) | $5 / $30 | $0.1 / $0.3 | StepFun: Step 3.5 Flash |
| Cache Read Price (per 1M) | $2.5/1M (50% Off) | $0.05/1M (50% Off) | StepFun: Step 3.5 Flash |
| Context Window / Max Output | 1000K In / 128K Out | 256K In / 64K Out | OpenAI GPT-5.5 |
| P90 First-Token / Edge Latency | 320ms | 280ms | StepFun: Step 3.5 Flash (-40ms) |
Flagship GPT-5 series general model with configurable reasoning_effort from none to xhigh.
Step 3.5 Flash is StepFun's most capable open-source foundation model. Built on a sparse Mixture of Experts (MoE) architecture, it selectively activates only 11B of its 196B parame
Real-Time Stack Cost & Hidden-Fee Simulator (MAU / Token / Egress / GMV)
Calibrated with Reddit r/FinOps & r/devops telemetry: Includes Context Caching, Bandwidth Egress, and MoR Tax
🛰️Switch from OpenAI GPT-5.5 to StepFun: Step 3.5 Flash
Step 3.5 Flash is StepFun's most capable open-source foundation model. Built on a sparse Mixture of Experts (MoE) architecture, it selectively activates only 11B of its 196B parame Verified P90 latency of 280ms.