14 4K posters: FLUX.3 vs Nano Banana 2.1 vs GPT Image 2.5 on Sume

Fourteen 4K posters cost $8.498 on FLUX.3 at Black Forest Labs' list price, $2.80 on Nano Banana 2.1 through Sume and $3.115 on GPT Image 2.5 at high quality through Sume. Sume does not list FLUX.3 yet, so the FLUX.3 figure is a price you would pay BFL directly, not through Sume.

Prices per 4K image

FLUX.3 Image went live on BFL's API on 2026-10-01 with four resolution tiers. The 4k tier is roughly 16 megapixels. BFL prices in credits, where one credit equals $0.01. Sume's two rows come from its public catalog.

The 2k to 4k step on FLUX.3

BFL's own tiers show how steep the 4k step is: the 2k tier is $0.100 and the 4k tier is $0.607, a factor of 6.07. If your posters print at A3 or smaller, 2k may be enough, and 14 posters at 2k would cost $1.40 on BFL. That is a separate decision from the model choice, and it is one only FLUX.3 forces on you, because on Sume the Nano Banana 2.1 price moves from $0.15 at 2K to $0.20 at 4K.

What this means for a Sume user

Because FLUX.3 is not in Sume's catalog, there is no way to request it through a Sume key. The honest comparison for a Sume user is between the two image models that are listed. Nano Banana 2.1 at 4K is cheaper per image than GPT Image 2.5 at high quality, by $0.0225 per image, or $0.315 over the 14 posters ($3.115 minus $2.80).

GPT Image 2.5 has features the Sume Image API documents that matter for posters: up to 16 image references, an optional mask, and a transparent or opaque background option. Neither price includes the cost of retries, so budget for a reroll or two per poster.

• FLUX.3 is only on BFL today, per Sume's catalog.
• Nano Banana 2.1 4K is the lower Sume price for this job.
• Re-check both pages the day you run the batch.

Reproduce the numbers

Every Sume price on this page comes from the public catalog at https://api.sume.com/v1/catalog, which needs no API key. Fetch it, find the row for the job or model named in the table, and multiply by your own seconds, characters or image count. Sume bills the list price shown in that row, so the catalog figure is the one that applies to your balance.

Vendor figures were read from Black Forest Labs pricing docs on 2026-10-09 and are the vendor's to change. Where a vendor page did not show a number, this page leaves it out instead of guessing, and any assumption that is ours is labeled as one.