24 children's book pages at 4K: $4.80 or $5.34 on Sume

The short answer

Twenty-four full-page illustrations at 4K cost $4.80 on Sume with Nano Banana 2.1 (24 x $0.20) and $5.34 with GPT Image 2.5 high (24 x $0.2225 = $5.34). At 2K the Nano Banana 2.1 total is $3.60 and GPT Image 2.5 medium is $1.34.

Print is where the 4K price matters, and it is the one tier where the Sume premium over Google is smallest: $0.20 against Google's $0.113 is a factor of 1.77, against 2.98 at 1K and 2K.

The arithmetic

A standard picture book has 24 to 32 pages. The table prices exactly 24 images, one per page, so add a row if your cover and endpapers are separate. A re-do rate of one in four would be six extra images.

The price ratios come straight from the numbers: $0.20 divided by $0.113 is 1.77, and $0.10 divided by $0.0336 is 2.98.

How to run it

Use a low or 0.5K draft of each page for layout approval and spend the 4K price only on the approved pages. A draft costs $0.075 on Nano Banana 2.1 at 0.5K or $0.02475 on GPT Image 2.5 low.

Character consistency is the hard part of a picture book. Feed the approved character image back as an input reference on every page instead of describing the character in words each time.

Retries and cost per page

Some images will be rejected by eye, and rejected images are billed like any other, so budget a margin. The bullets add 20 percent to each Sume total in the table above (the totals multiplied by 1.2) and divide by the number of pages to give a per-page cost.

Treat the per-page figure as the number to compare across models, because it does not change when the count changes. Re-read the public catalog before a large run, since prices can change and the table is a snapshot from 2026-10-08.

• Nano Banana 2.1 at 4K: $4.80 becomes $5.76 with 20 percent extra images, which is $0.24 per page (a 24-page job).
• GPT Image 2.5 high (4K): $5.34 becomes $6.41 with 20 percent extra images, which is $0.27 per page (a 24-page job).
• Nano Banana 2.1 at 2K: $3.60 becomes $4.32 with 20 percent extra images, which is $0.18 per page (a 24-page job).
• GPT Image 2.5 medium (2K): $1.34 becomes $1.61 with 20 percent extra images, which is $0.07 per page (a 24-page job).

What the docs say to check

Check the status code, not the body shape. POST /v1/images waits up to 30 seconds and returns the images with 200. Slow settings (4K, high quality, a large n) are the most likely to come back as 202 with a job envelope, and you then read the images from the job result endpoint described in Jobs and results.

On GPT Image 2.5 the quality values are auto, low, medium, high, xhigh and max. If you omit quality the default is high, and auto reserves max, so pin the tier you budgeted for instead of leaving it to the default.

For a printed run, check the pixel dimensions you receive against your printer's requirement before ordering, since the 4K tier is a normalized label and not a promise of one exact size.

Every price in this post is a snapshot dated 2026-10-08. The Sume figures come from the public catalog and the Image API docs, the Google figures come from its Gemini API pricing page, and no figure here is a benchmark of quality or speed. Prices and model lists change, so confirm them on the day you spend money.