# GPT-5.5 vs Meta Llama 3.1 405B Instruct

On provider list prices, Meta Llama 3.1 405B Instruct costs $3.50 per million input tokens against $5 for GPT-5.5: 1.4x apart. Output is $3.50 against $30 (8.6x). On Allocate both bill at list plus the 7% transaction fee.

## Specifications

| | GPT-5.5 | Meta Llama 3.1 405B Instruct |
| --- | --- | --- |
| Lab | OpenAI | Meta |
| Access | API only | Open weights |
| Context window | 400K tokens | 4K tokens |
| List price, input | $5 / M tokens | $3.50 / M tokens |
| List price, output | $30 / M tokens | $3.50 / M tokens |
| Cached input | $0.50 / M tokens | n/a |
| License | Proprietary API | Llama community |
| Fine-tunable | No | Yes |

Specifications and provider list prices from the Allocate catalog, checked 2026-07-08. Billed price is list plus the 7% transaction fee.

## What the numbers say

Take 1,000,000 requests a month at 1,200 input and 350 output tokens each. That workload costs $5,425 a month on Meta Llama 3.1 405B Instruct and $16,500 on GPT-5.5 at list: a gap of $11,075, or 3.0x.

GPT-5.5 reads 400K tokens per request against 4K for Meta Llama 3.1 405B Instruct, 97.7x the window. That decides which one can take whole documents without splitting them.

## Choose GPT-5.5 for

- Complex tool-using agents
- Code generation
- General assistants

## Choose Meta Llama 3.1 405B Instruct for

- The lower list price ($3.50 in / $3.50 out per M tokens)
- Open weights you can fine-tune and own

## Common questions

### Which is cheaper, GPT-5.5 or Meta Llama 3.1 405B Instruct?

Meta Llama 3.1 405B Instruct, on this workload shape. At list prices it is $3.50/$3.50 per million tokens in and out against $5/$30 for GPT-5.5. Billed on Allocate: $3.75/$3.75 against $5.35/$32.10, list plus 7%.

### Which has the bigger context window?

GPT-5.5: 400,000 tokens (400K) against 4,096 (4K) for Meta Llama 3.1 405B Instruct.

### Can I fine-tune GPT-5.5 or Meta Llama 3.1 405B Instruct?

Meta Llama 3.1 405B Instruct publishes open weights (Llama community) and can be fine-tuned on your own data. GPT-5.5 is a closed model served over API; its weights are not available.

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[HTML page](https://allocate.network/compare/gpt-5-5-vs-meta-llama-3-1-405b-instruct) · [GPT-5.5](https://allocate.network/models/gpt-5-5.md) · [Meta Llama 3.1 405B Instruct](https://allocate.network/models/meta-llama-3-1-405b-instruct.md) · [Machine-readable catalog](https://allocate.network/catalog.json)