Imagen 4 Ultra or Nano Banana 2.1 at 0.5K: both $0.075 on Sume

Imagen 4 Ultra and Nano Banana 2.1 at the 0.5K tier cost the same on Sume, $0.075 per image, so pick by what you need to do with the image. Imagen 4 Ultra is text-to-image only. Nano Banana 2.1 also edits and takes up to 10 reference images.

The numbers

Imagen 4 Ultra has a provider price of $0.06 in the Sume pricing tables; Nano Banana 2.1 at 0.5K is also $0.06. Sume bills provider price x 1.25, so both land at $0.075. Google's own Imagen page now says Imagen models are shut down in the Gemini API and points to Nano Banana, yet Sume still lists the Imagen 4 rows, so check the catalog for the current state before you build on them.

When to take Imagen 4 Ultra

Take it for a pure text prompt where you already like its look and a 1K or 2K frame is what you want. If the row ever leaves the catalog, a pinned id will fail, so read GET /v1/images/models at startup.

When to take Nano Banana 2.1

Take it when a second pass is likely: fix a label, swap a background, recolor. The same model that drew the draft can edit it, and you can raise the resolution later: 1K is $0.10, 2K $0.15, 4K $0.20. Google also lists search-grounded generation for it, but the Sume parameter list for the row has no grounding field, so do not plan on it.

A default

For a first pass where you are unsure, start at Nano Banana 2.1 0.5K. You pay the same as Imagen 4 Ultra and keep the option to edit.

How to run the comparison

Take 10 prompts you already use and run each once on google/imagen-4-ultra and once on google/nano-banana-2.1 at 0.5K. The cost is 10 x $0.075 = $0.75 per model, $1.50 for both. Look at three things: how close each image is to the prompt, how clean the details are at the size you ship, and whether you wanted to touch up the result.

If Imagen wins on look, you lose nothing by using it for first drafts. If you then need a change, such as a different label, take the winner into Nano Banana 2.1 as a reference and edit it. That is the two-step flow in the draft-then-edit post.

At the same price the tie-breaker is risk. Google's Imagen page says Imagen is shut down in its own API, while Nano Banana 2.1 is the model Google prices on the same page. Keep an Imagen-free fallback in your config.

This post compares catalog limits and prices only. It does not claim that either model looks better, and no benchmark is cited. Google's pricing page says Nano Banana 2.1 improves visual quality, prompt adherence and text rendering over Nano Banana 2, which is a statement about 2.1 against its predecessor, not against Imagen.

Prices change. The $0.075 figures are Sume list as of 2026-10-08, computed as the provider price of $0.06 times 1.25. If the provider price moves, both rows move with their own tables, and they may stop being equal. Read pricing from the endpoints route when the number matters, and save the date with it.