Source-tracked model comparison

How do GPT-5.6 Luna and Gemini 2.5 Flash costs compare for developer assistance?

Compare verified pricing and model limits for mid-volume developer assistance. The cost example uses a developer assistant backend workload and does not assume equal model quality.

Direct cost answer: gpt-5.6-luna is estimated at $655.00 per month and Gemini 2.5 Flash at $249.00 for 5,000 input tokens, 1,500 output tokens, and 50,000 monthly requests. Gemini 2.5 Flash is $406.00 lower under these assumptions. This does not identify a quality winner.
low priorityobserveSources checked 2026-07-13 / 2026-07-12
Tracked facts

Pricing and model limits

Prices are USD per 1M tokens under each model's verified default profile.

Fieldgpt-5.6-lunaGemini 2.5 Flash
ProviderOpenAIGoogle
API model IDgpt-5.6-lunagemini-2.5-flash
Input / 1M$1.00$0.30
Cached input / 1M$0.10$0.03
Output / 1M$6.00$2.50
Context window1,050,000 tokens1,048,576 tokens
Maximum output128,000 tokens65,536 tokens
Accepted inputtext, imagetext, image, video, audio
Example workload

Developer assistant backend cost scenario

5,000 input and 1,500 output tokens per request, 50,000 monthly requests, and 20% cached input.

OpenAI

gpt-5.6-luna

$655.00 / month
Input cost
$205.00
Output cost
$450.00
Per 1,000 calls
$13.10
Pricing profile
standard / short context
View model details
Google

Gemini 2.5 Flash

$249.00 / month
Input cost
$61.50
Output cost
$187.50
Per 1,000 calls
$4.98
Pricing profile
standard / text
View model details

Cost result: Gemini 2.5 Flash is $406.00 lower per month for these assumptions. This is a price comparison, not a model-quality ranking.

StackLens assessment

Questions to answer before choosing

  • Which model handles the team's real code context more consistently?
  • Do existing cloud and SDK choices reduce switching work?
  • How much cached context is reusable in normal sessions?
Workload caveat

What this estimate leaves out

The calculation does not compare coding quality and excludes indexing, execution sandboxes, and repository storage.

Latency, reliability, output quality, retries, regional processing, and provider-specific tool charges can change the practical decision.