Solar Pro 4 is $1.47 cheaper per 1M input tokens (98% lower; 50x difference).
API cost decision in 10 seconds
Solar Pro 4 vs Gemini 3.5 Flash
Pick Solar Pro 4 for lower cost; pick Gemini 3.5 Flash only if the larger context window matters more.
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Data confirmed:
Prices normalized to USD per 1M tokens
Sample workload: 1M input + 500K output
Budget verdict
Pick Solar Pro 4 for lower cost; pick Gemini 3.5 Flash only if the larger context window matters more.
On the standard 1M input plus 500K output workload, Solar Pro 4 is estimated at $0.09 vs $6 for Gemini 3.5 Flash, saving $5.91 (98.5% lower).
Cost-first pickSolar Pro 4
Context-first pickGemini 3.5 Flash
Sample savings$5.9198.5%
10x traffic gap$59.1
Gemini 3.5 Flash has more context, but Solar Pro 4 saves $5.91 on the standard workload. At 10x that traffic, the same price gap is about $59.1. Use the calculator below to replace the sample workload with your own token volume.
Cost sensitivity
Workload Sensitivity
Solar Pro 4 stays cheaper across input-heavy, balanced, and output-heavy sample workloads.
| Workload shape | Token mix | Better pick | Solar Pro 4 | Gemini 3.5 Flash |
|---|---|---|---|---|
| Input-heavy / RAG | 5M input + 500K output | Solar Pro 4 | $0.21 | $12 |
| Balanced workload | 1M input + 1M output | Solar Pro 4 | $0.15 | $10.5 |
| Output-heavy chatbot | 1M input + 5M output | Solar Pro 4 | $0.63 | $46.5 |
Solar Pro 4 is $8.88 cheaper per 1M output tokens (98.7% lower; 75x difference).
Gemini 3.5 Flash has 524.29K more context (2x larger).
Solar Pro 4 is $5.91 cheaper on the standard workload (98.5% lower).
Estimate your workload cost
Your Workload Cost
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
Solar Pro 4 has the lower input price; Solar Pro 4 has the lower output price; Gemini 3.5 Flash offers the larger context window. For the 1M input plus 500K output sample, Solar Pro 4 is cheaper for the standard workload.
For a 1M input token plus 500K output token workload, the estimated API cost is $0.09 for Solar Pro 4 and $6 for Gemini 3.5 Flash.
Choose Solar Pro 4 when you care most about lower input-token price, and lower output-token price.
Choose Gemini 3.5 Flash when you care most about larger context window.
- On the standard 1M input plus 500K output workload, Solar Pro 4 is estimated at $0.09 vs $6 for Gemini 3.5 Flash, saving $5.91 (98.5% lower).
- Solar Pro 4 is $5.91 cheaper on the standard workload (98.5% lower).
- Solar Pro 4 is $1.47 cheaper per 1M input tokens (98% lower; 50x difference).
- Solar Pro 4 is $8.88 cheaper per 1M output tokens (98.7% lower; 75x difference).
- Gemini 3.5 Flash has 524.29K more context (2x larger).
| Feature | Solar Pro 4 (Upstage) | Gemini 3.5 Flash (Google) |
|---|---|---|
| Input Price prompt tokens per 1M | $0.03 | $1.5 |
| Completion Price per 1M tokens | $0.12 | $9 |
| Sample Workload Cost 1M input + 500K output | $0.09 | $6 |
| Context Window | 524.29K | 1.05M |
| Release Date |
Use-Case Decision Matrix
| Use case | Better pick | Why |
|---|---|---|
| Budget-constrained production | Solar Pro 4 | On the standard 1M input plus 500K output workload, Solar Pro 4 is estimated at $0.09 vs $6 for Gemini 3.5 Flash, saving $5.91 (98.5% lower). |
| High-volume input processing | Solar Pro 4 | Lower prompt-token price matters most when prompts, retrieved passages, or documents dominate the bill. |
| Long responses and chatbots | Solar Pro 4 | Lower output-token price matters most when assistants generate many completion tokens. |
| RAG or long-document work | Gemini 3.5 Flash | A larger context window leaves more room for retrieved passages, conversation history, or source files. |
Related Alternatives
- Gemma 4 26B A4B (free) can replace Gemini 3.5 Flash when lower sample workload cost matters most: $0.
- Gemma 4 31B (free) can replace Gemini 3.5 Flash when lower sample workload cost matters most: $0.
- Lyria 3 Pro Preview can replace Gemini 3.5 Flash when lower sample workload cost matters most: $0.
- Lyria 3 Clip Preview can replace Gemini 3.5 Flash when lower sample workload cost matters most: $0.
- Grok 4.20 Multi-Agent offers 2M context with $2.5 sample workload cost.
- Grok 4.20 offers 2M context with $2.5 sample workload cost.
- DeepSeek V4 Flash 0731 offers 1.31M context with $0.17 sample workload cost.
- DeepSeek V4 Flash Latest offers 1.31M context with $0.11 sample workload cost.
- DeepSeek V4 Flash 0731 · DeepSeek · #1
- MiMo-V2.5 · Xiaomi · #2
- Hy3 · Tencent · #3
- Ox Alpha · stealth · #4
Cheaper alternatives
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Open cheapest modelsLarger context alternatives
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Open provider hubsUpstage catalog
Review all tracked Upstage models before deciding whether this matchup is the right shortlist.
Open Upstage modelsGoogle catalog
Check other Google models with comparable pricing, context, or release timing.
Open Google modelsSolar Pro 4 is Upstage's cost-efficient large language model, featuring a 524K context window. It is built for long-horizon tasks and agentic workflows, with strong capabilities in office productivity, document-intensive...
Gemini 3.5 Flash is Google's high-efficiency multimodal model, bringing near-Pro level coding and reasoning at Flash-tier cost and speed. It is highly optimized for coding proficiency and parallel agentic execution...