GPT-5.5 Pro vs Llama 3.1 405B (Together AI): API Cost Comparison
Compare the API pricing, context windows, features, and real-world cost projections for GPT-5.5 Pro (OpenAI) and Llama 3.1 405B (Together AI) (Together AI). Use the interactive calculator below to compute your exact monthly cost based on your token usage and request volume.
Prices verified Apr 30, 2026
Interactive Cost Calculator
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Showing costs for 2 models. Cheapest: Llama 3.1 405B (Together AI) at $52.50/month.
| Alert | |||||||
|---|---|---|---|---|---|---|---|
BestLlama 3.1 405B (Together AI) | Together AI | $52.50 | $0.005250 | $35.00 | $17.50 | 95.6% | Alerts coming soon |
GPT-5.5 Pro | OpenAI | $1,200.00 | $0.120000 | $300.00 | $900.00 | — | Alerts coming soon |
Monthly Cost Comparison
Price Comparison at a Glance
All prices are in USD per 1 million tokens ($/M tokens). Lower is cheaper.
| Pricing Type | GPT-5.5 Pro | Llama 3.1 405B (Together AI) | Cheaper |
|---|---|---|---|
| Input (standard) | $30.00/M | $3.50/M | Llama 3.1 405B (Together AI) |
| Output | $180.00/M | $3.50/M | Llama 3.1 405B (Together AI) |
Prices last verified: 2026-03-06 – 2026-04-30
Cost Breakdown by Usage Volume
Estimated monthly costs at different request volumes, assuming 1,000 input tokens and 500 output tokens per request. Adjust in the calculator above for your specific use case.
| Volume | GPT-5.5 ProMonthly | Llama 3.1 405B (Together AI)Monthly | GPT-5.5 ProPer request | Llama 3.1 405B (Together AI)Per request |
|---|---|---|---|---|
| 1K requests/mo | $120.00 | $5.25 | $0.120000 | $0.005250 |
| 10K requests/mo | $1,200.00 | $52.50 | $0.120000 | $0.005250 |
| 100K requests/mo | $12,000.00 | $525.00 | $0.120000 | $0.005250 |
| 1M requests/mo | $120,000.00 | $5,250.00 | $0.120000 | $0.005250 |
Green values indicate the lower-cost option at each volume tier. Cost per request is calculated at 1,000 input + 500 output tokens using standard (non-batch, non-cached) pricing.
Price History
Input price per 1M tokensWhen to Choose GPT-5.5 Pro
by OpenAI
- General chatbot
Input / 1M tokens
$30.00/M
Output / 1M tokens
$180.00/M
Context window
1,050,000
Tier
premium
When to Choose Llama 3.1 405B (Together AI)
by Together AI
- Code generation
- Content & copywriting
- Document summarization
Input / 1M tokens
$3.50/M
Output / 1M tokens
$3.50/M
Context window
131,072
Tier
premium
Key Differences Beyond Price
Cost is only one factor in choosing an AI model. Context window size, rate limits, supported features, and latency all affect whether a model fits your use case.
| Capability | GPT-5.5 Pro | Llama 3.1 405B (Together AI) |
|---|---|---|
| Context window | 1,050,000 tokens | 131,072 tokens |
| Max output tokens | 128,000 tokens | 4,096 tokens |
| Performance tier | Premium | Premium |
| Vision / image input | Yes | No |
| Function calling | Yes | Yes |
| JSON mode | Yes | Yes |
| Prompt caching | No | No |
| Batch API (50% discount) | No | No |
| Extended reasoning | Yes | No |
| Fine-tuning | No | No |
Llama 3.1 405B (Together AI) notes
Largest open-source model available via API. Meta license allows commercial use.
Frequently Asked Questions
Is GPT-5.5 Pro cheaper than Llama 3.1 405B (Together AI)?
At standard usage (1,000 input tokens, 500 output tokens, 100,000 requests/month), Llama 3.1 405B (Together AI) costs $525.00/month versus $12,000.00/month for GPT-5.5 Pro — a 96% saving. Your actual savings will vary based on your token profile; output-heavy workloads amplify differences in output pricing.
Which model has a larger context window, GPT-5.5 Pro or Llama 3.1 405B (Together AI)?
GPT-5.5 Pro has a larger context window at 1,050,000 tokens, compared to 131,072 tokens for Llama 3.1 405B (Together AI). A larger context window is important for processing long documents, multi-turn conversations, or large codebases without truncation.
Do GPT-5.5 Pro and Llama 3.1 405B (Together AI) support the Batch API?
Neither GPT-5.5 Pro nor Llama 3.1 405B (Together AI) currently supports a batch API with discounted pricing. For batch-eligible alternatives, consider models from OpenAI, Anthropic, or Google that include batch API support.
Which model offers better prompt caching?
Neither GPT-5.5 Pro nor Llama 3.1 405B (Together AI) currently supports prompt caching. For prompt-caching capable alternatives, consider Claude models from Anthropic or GPT-4o from OpenAI.
What are the best use cases for GPT-5.5 Pro vs Llama 3.1 405B (Together AI)?
GPT-5.5 Pro is best suited for General chatbot, while Llama 3.1 405B (Together AI) is optimized for Code generation, Content & copywriting, Document summarization. Choose based on which use case matches your primary workload — and validate with the cost calculator above to confirm the total monthly spend fits your budget.
What is the cost per request for GPT-5.5 Pro vs Llama 3.1 405B (Together AI)?
At 1,000 input tokens and 500 output tokens per request — a typical conversational workload — GPT-5.5 Pro costs $0.120000 per request and Llama 3.1 405B (Together AI) costs $0.005250 per request. At 100,000 requests/month, that translates to $12,000.00 and $525.00 respectively. Use the interactive calculator to adjust these parameters for your actual workload.
GPT-5.5 Pro vs Llama 3.1 405B (Together AI): Summary
When comparing GPT-5.5 Pro and Llama 3.1 405B (Together AI) for API cost, the right choice depends on your workload's token profile, required features, and tolerance for latency. Llama 3.1 405B (Together AI) offers lower total cost at standard usage volumes (1,000 input + 500 output tokens per request at 100,000 requests/month) at $525.00/month, compared to $12,000.00/month for GPT-5.5 Pro.
Both models are priced in USD per million tokens, the standard unit across all major AI API providers. GPT-5.5 Pro charges $30.00/M for input tokens and $180.00/M for output tokens. Llama 3.1 405B (Together AI) charges $3.50/M input and $3.50/M output. If your workload is output-heavy (more tokens generated than consumed as input), the model with the lower output price compounds cost savings significantly at scale.
Context window capacity differs between the two: GPT-5.5 Pro supports up to 1,050,000 tokens in a single request, versus 131,072 tokens for Llama 3.1 405B (Together AI). A larger context window is essential for document summarization, large codebase analysis, and multi-document retrieval-augmented generation (RAG) applications.
Use the interactive calculator at the top of this page to enter your actual token usage and monthly request volume for a precise cost comparison tailored to your workload. Adjust for batch API discounts and prompt caching to find the most cost-effective option for your specific deployment.
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