API cost decision in 10 seconds

Step 3.5 Flash vs gpt-oss-20b

Pick gpt-oss-20b for lower cost; pick Step 3.5 Flash only if the larger context window matters more.

Page updated: 2026-05-26T15:08:08Z Data confirmed: 2026-05-26T19:08:13Z Prices normalized to USD per 1M tokens Sample workload: 1M input + 500K output

Budget verdict

Pick gpt-oss-20b for lower cost; pick Step 3.5 Flash only if the larger context window matters more.

On the standard 1M input plus 500K output workload, gpt-oss-20b is estimated at $0.1 vs $0.24 for Step 3.5 Flash, saving $0.14 (58.3% lower).

Cost-first pickgpt-oss-20b

Context-first pickStep 3.5 Flash

Sample savings$0.1458.3%

10x traffic gap$1.4

Step 3.5 Flash has more context, but gpt-oss-20b saves $0.14 on the standard workload. At 10x that traffic, the same price gap is about $1.4. Use the calculator below to replace the sample workload with your own token volume.

Cost sensitivity

Workload Sensitivity

Same prices, different token mixes.

gpt-oss-20b stays cheaper across input-heavy, balanced, and output-heavy sample workloads.

Workload shape	Token mix	Better pick	Step 3.5 Flash	gpt-oss-20b
Input-heavy / RAG	5M input + 500K output	gpt-oss-20b	$0.6	$0.22
Balanced workload	1M input + 1M output	gpt-oss-20b	$0.39	$0.17
Output-heavy chatbot	1M input + 5M output	gpt-oss-20b	$1.59	$0.73

Cheaper input gpt-oss-20b $0.09 vs $0.03 / 1M

gpt-oss-20b is $0.06 cheaper per 1M input tokens (66.7% lower; 3x difference).

Cheaper output gpt-oss-20b $0.3 vs $0.14 / 1M

gpt-oss-20b is $0.16 cheaper per 1M output tokens (53.3% lower; 2.14x difference).

Larger context Step 3.5 Flash 262.14K vs 131.07K

Step 3.5 Flash has 131.07K more context (2x larger).

Sample workload gpt-oss-20b $0.24 vs $0.1

gpt-oss-20b is $0.14 cheaper on the standard workload (58.3% lower).

Estimate your workload cost

Your Workload Cost

Prices are normalized to USD per 1M tokens.

Monthly input tokens Monthly output tokens

Step 3.5 Flash Calculating… Estimated API cost

gpt-oss-20b Calculating… Estimated API cost

Cheaper for this workload Calculating… Difference: calculating…

This estimate uses normalized public API pricing per 1M tokens. It is a planning aid, not a billing quote. Verify provider pricing, limits, and terms before production use.

Quick Decision

Verdict

gpt-oss-20b has the lower input price; gpt-oss-20b has the lower output price; Step 3.5 Flash offers the larger context window. For the 1M input plus 500K output sample, gpt-oss-20b is cheaper for the standard workload.

For a 1M input token plus 500K output token workload, the estimated API cost is $0.24 for Step 3.5 Flash and $0.1 for gpt-oss-20b.

Best Fit

Choose Step 3.5 Flash when you care most about larger context window.

Choose gpt-oss-20b when you care most about lower input-token price, and lower output-token price.

Decision Notes

On the standard 1M input plus 500K output workload, gpt-oss-20b is estimated at $0.1 vs $0.24 for Step 3.5 Flash, saving $0.14 (58.3% lower).
gpt-oss-20b is $0.14 cheaper on the standard workload (58.3% lower).
gpt-oss-20b is $0.06 cheaper per 1M input tokens (66.7% lower; 3x difference).
gpt-oss-20b is $0.16 cheaper per 1M output tokens (53.3% lower; 2.14x difference).
Step 3.5 Flash has 131.07K more context (2x larger).

Head-to-Head Specs

Feature	Step 3.5 Flash (StepFun)	gpt-oss-20b (OpenAI)
Input Price prompt tokens per 1M	$0.09	$0.03
Completion Price per 1M tokens	$0.3	$0.14
Sample Workload Cost 1M input + 500K output	$0.24	$0.1
Context Window	262.14K	131.07K
Release Date	2026-01-29	2025-08-05
Popularity	#43	#67

Use-Case Decision Matrix

Use case	Better pick	Why
Budget-constrained production	gpt-oss-20b	On the standard 1M input plus 500K output workload, gpt-oss-20b is estimated at $0.1 vs $0.24 for Step 3.5 Flash, saving $0.14 (58.3% lower).
High-volume input processing	gpt-oss-20b	Lower prompt-token price matters most when prompts, retrieved passages, or documents dominate the bill.
Long responses and chatbots	gpt-oss-20b	Lower output-token price matters most when assistants generate many completion tokens.
RAG or long-document work	Step 3.5 Flash	A larger context window leaves more room for retrieved passages, conversation history, or source files.

Related Alternatives

Same-provider lower-cost swaps

gpt-oss-120b (free) can replace gpt-oss-20b when lower sample workload cost matters most: $0.
gpt-oss-20b (free) can replace gpt-oss-20b when lower sample workload cost matters most: $0.

Larger context near this budget

Llama 4 Scout offers 10M context with $0.23 sample workload cost.
Owl Alpha offers 1.05M context with $0 sample workload cost.
DeepSeek V4 Flash offers 1.05M context with $0.2 sample workload cost.
MiMo-V2.5 offers 1.05M context with $0.28 sample workload cost.

Popular competitors

DeepSeek V4 Flash · DeepSeek · #1
Hy3 preview · Tencent · #2
Claude Opus 4.7 · Anthropic · #3
Claude Sonnet 4.6 · Anthropic · #4

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Provider catalogs

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StepFun catalog

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OpenAI catalog

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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 parameters per token....

gpt-oss-20b

gpt-oss-20b is an open-weight 21B parameter model released by OpenAI under the Apache 2.0 license. It uses a Mixture-of-Experts (MoE) architecture with 3.6B active parameters per forward pass, optimized for...