Image Studio uses the image credit pool (9 HKD per 100 credits for individual top-ups). Each generation charges:

total credits = credits_per_image × number_of_images (1–4)

Credits are checked before generation starts and deducted only after images successfully complete (see When credits are not used).

Top-up rate

Target margin on paid usage is ~25% after fal.ai generation cost.

Credits by model

Rates below are per image at the listed size/quality. GPT Image 2 custom sizes above ~2.5K pixels apply a ×2 multiplier on the quality rate.

Nano Banana family

GPT image models

Flux

Worked examples

In HKD (individual top-up rate): 26 credits ≈ 2.34 HKD per high GPT Image 2 image.

Also uses image credits

These features draw from the same image pool, not chat credits:

• Tutor Studio — slide images, infographics
• Image Generate Studio — all models above

In-chat image generation via agent tools uses chat credits (10 per image) instead.

School defaults

Each school member starts with a 100 image credit plan-base cap (before admin bonus assignment). Monthly resets return caps to the school default unless the admin has raised them.

See School credits: users, top-up & assign for how admins buy pool packs and assign extra caps.

Rates follow fal.ai provider costs and may be updated via backend migrations. The live credit estimate in Image Studio is always authoritative.