Gemini 3.1 Pro API pricing

Gemini 3.1 Pro cost by workload

Effective cost uses the minimum 2× credit.

How Gemini 3.1 Pro pricing works

You are charged per token: 2 USD per million tokens you send and 12 USD per million tokens Gemini writes back. Output is 6.0× the input rate for Gemini 3.1 Pro, so answer length drives most of the bill.

Somnus bills usage at the list price and credits every top-up at 2× or more, which is how the effective $1 / $6 rate comes about.

Estimate Gemini 3.1 Pro cost from the usage field

from openai import OpenAI
import os

client = OpenAI(
    api_key=os.environ["SOMNUS_API_KEY"],
    base_url="https://gateway-production-c837.up.railway.app/v1",
)

resp = client.chat.completions.create(
    model="claude-sonnet-5",
    messages=[
      {"role": "user", "content": "Count my tokens"}
    ],
)
print(resp.choices[0].message.content)

Multiply usage.prompt_tokens by 2/1e6 and usage.completion_tokens by 12/1e6.

Questions

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