fix(cost_calculator): correct gpt-image-1 cost calculation using token-based pricing

[Chesars]

Title

fix(cost_calculator): correct gpt-image-1 cost calculation using token-based pricing

Relevant issues

Fixes #13847

Pre-Submission checklist

• I have Added testing in the tests/litellm/ directory
• My PR passes all unit tests on make test-unit
• My PR's scope is as isolated as possible, it only solves 1 specific problem

Type

🐛 Bug Fix

Changes

Summary

The current cost calculator for gpt-image-1 uses pixel-based pricing (inherited from DALL-E), but OpenAI's gpt-image-1 actually uses token-based pricing.

Example

import litellm

response = litellm.image_generation(
    model="gpt-image-1",
    prompt="A cat sitting on a windowsill",
    size="1024x1024",
    quality="medium",
)

# Response includes usage data:
# response.usage.input_tokens = 150
# response.usage.output_tokens = 8000
# response.usage.input_tokens_details.text_tokens = 150
# response.usage.input_tokens_details.image_tokens = 0

# Cost with this fix is calculated correctly using tokens
cost = litellm.completion_cost(completion_response=response)
# Returns: $0.32075 (not $0.042 as before)

Old calculation (incorrect - DALL-E style):

cost = input_cost_per_pixel × width × height × n
cost = 4.0054321e-08 × 1024 × 1024 × 1 = $0.042

New calculation (token-based):

# OpenAI gpt-image-1 pricing:
# - Text Input: $5.00/1M tokens
# - Image Input: $10.00/1M tokens  
# - Image Output: $40.00/1M tokens

Solution

1. Updated pricing JSON: Changed gpt-image-1 entries from input_cost_per_pixel to token-based fields:

   • input_cost_per_token: 5e-06 ($5/1M)
   • input_cost_per_image_token: 1e-05 ($10/1M)
   • output_cost_per_image_token: 4e-05 ($40/1M)

2. New cost calculator: litellm/llms/openai/image_generation/cost_calculator.py

   • Uses usage data from the API response
   • Calculates: text_input + image_input + image_output costs

3. Updated router: Routes gpt-image-1 models to the new token-based calculator while DALL-E continues to use pixel-based calculation

Files changed

• model_prices_and_context_window.json - Updated gpt-image-1 pricing
• litellm/model_prices_and_context_window_backup.json - Same
• litellm/llms/openai/image_generation/cost_calculator.py - New calculator
• litellm/litellm_core_utils/llm_cost_calc/utils.py - Router update
• tests/test_litellm/test_gpt_image_cost_calculator.py - 8 new tests

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Project	Deployment	Review	Updated (UTC)
litellm	Ready	Preview, Comment	Dec 12, 2025 10:19pm