Transparent sticker: GPT Image 2.5 background field or Nano Banana 2.1

For a transparent sticker, ChatGPT Image 2.5 is the Sume image row that takes a background field (auto, transparent or opaque). Nano Banana 2.1 does not list that field, so a transparent PNG from it means a second step: $0.10 for the image at 1K plus $0.0225 for background removal, $0.1225 in all.

What the catalog lists

The Sume docs say ChatGPT Image 2.5 supports background, and the catalog code adds it only to the two GPT Image 2.5 rows. A request that sets a parameter a model does not list returns 400 unsupported_parameter rather than ignoring it.

Which to use

If you make hundreds of stickers, price both. The GPT row costs depend on quality and size, so quote one sample before multiplying. The two-step path has a fixed price you can compute up front, but it adds a second job to track and the cut-out edge can be rough on hair or glass.

Prompt tip

Ask for a flat, single-color or white background and a clear outline when you plan to cut it out later, and keep shadows off the ground plane. A clean cut starts with a clean source.

Checking a cut-out

Put each result on a dark and a light background and look at the edge. Halos show up on one of them. If the edge fails, regenerate with a plainer background rather than fixing it by hand, because at $0.10 or less a retry is cheaper than editing time.

For GPT Image 2.5, request output_format: "png" when the background is transparent. Sume lists png, jpeg and webp for the row, and a transparent image needs an alpha channel, which JPEG does not have.

Price a pilot of 20 stickers on each path before you commit a large run. The pilot costs about $2 to $3 and shows the failure rate.

Costs to remember

The GPT Image 2.5 path has no second step, but its price needs a quote because it is token-based. Request a single sticker with quality and image_size set, read usage.cost, then multiply. The two-step Nano Banana 2.1 path has a known price, $0.1225 at 1K, but two jobs.

Whichever path you take, store the original and the cut-out. If you later move to a different cut-out tool, you can redo the second step without paying for the image again.

For a small shop, a rough plan is 20 stickers a week. On the two-step path at 1K that is 20 x $0.1225 = $2.45 a week. At 0.5K it is 20 x $0.0975 = $1.95. A weekly total under $3 means the choice between paths is about quality and your time, not money. If you run 2,000 stickers, the same arithmetic gives $245.00 and $195.00, and the pilot is worth doing carefully.