Cheapest AI image API per image in October 2026: vendor rates

On the vendor pages read today, the lowest sticker prices are Runway's Muse Image at 1 credit (about $0.01), FLUX.2 [flex] at $0.024 per image on Black Forest Labs, and Gemini 3.1 Flash Lite Image at $0.0336 for a 1K image. They are not comparable one to one, because each page bills a different unit, so the honest answer is a short ladder rather than a single winner.

Below is what each page said on 2026-10-02, followed by how to turn a sticker price into a number you can put in a budget on Sume.

What do the vendor pages list per image?

Every number here comes from the vendor's own page. Where a page gives a range, the range is quoted, not a single point.

Why is the cheapest sticker price not the cheapest image?

Three things move the real cost. First, the unit: BFL's calculator scales by resolution, Google bills output tokens, and fal quotes a per-unit range that spans a 25x gap between its cheapest and dearest image models. Second, the resolution you actually need: a 512px draft and a 4K final are different products. Third, retries: the cost per keeper is the price divided by your keep rate, so a model that is half the price but needs twice the attempts costs the same.

A practical rule is to price the same prompt at the same output size on every candidate, then divide by the number of images you keep.

How do I get a real per-image number on Sume?

Sume bills a single USD wallet. For listed models, the per-image line comes from the endpoint record, and the image docs state that "Endpoint pricing lines are the amount charged to your wallet", with Sume's margin already applied, so cost_usd × n is what you pay. Read the line before you commit to a batch.

Image generation billing is all-or-nothing: a completed generation is billed in full, and a failed or cancelled one is not billed. That removes failed attempts from the cost-per-keeper math, though not the images you generate and then discard.

curl "https://api.sume.com/v1/images/models" \
  -H "Authorization: Bearer $SUME_API_KEY"

curl "https://api.sume.com/v1/images/models/bytedance-seed/seedream-4.5/endpoints" \
  -H "Authorization: Bearer $SUME_API_KEY"
# read endpoints[].pricing[].cost_usd, then multiply by n

What does Sume not do here?

Sume does not match another vendor's sticker price, and it does not publish a single cheapest image model: the answer depends on the model you pick and the resolution tier you request. The rule for listed SKUs is provider list price times 1.25, reserved from the wallet when you submit and settled when the job finishes. See Generation admission for the reserve and refund behavior.

If you are comparing, use the same size and quality on both sides, and compare the Sume endpoint line against the vendor's per-image figure for that exact tier. A Runway credit is $0.01, so Muse Image at 1 credit is a useful floor for the comparison, but check that the model is the one you want before you let price decide.