Is GPT Image 2.5 cheaper than Seedream 5.0 Lite? It depends on quality

ChatGPT Image 2.5 is cheaper than Seedream 5.0 Lite at low and medium quality and dearer at high on Sume. At 1024x1024 it costs $0.007375 at low and $0.0165 at medium, against a flat $0.04375 for Seedream 5.0 Lite; at high it costs $0.065875, which is 51 percent more than Seedream. The crossover sits between medium and high, so the answer to the question depends on the quality tier you request.

The reason is the billing shape. Seedream 5.0 Lite has one price per image whatever the ratio. ChatGPT Image 2.5 is billed from output tokens, and the tier and the image size set the token count.

The numbers at 1:1

All six ChatGPT Image 2.5 tiers are shown, with Seedream 5.0 Lite as the reference row. Prices are billed, which is the provider list price times 1.25. The 2.5 figures assume a 1024x1024 output, a short text prompt and no references.

Two traps in the comparison

The first is the default. If you omit quality on ChatGPT Image 2.5, Sume's default is high, so a request that does not set the tier lands on the 151 percent row, not the cheap one. Set quality: "medium" explicitly when you mean medium.

The second is shape. The 2.5 prices fall for ratios with a shorter short side, so a 16:9 or 4:5 image is cheaper than the square one above. Seedream's price does not move. That widens the gap in 2.5's favour at low and medium and narrows it at high.

What to pick by job

For drafts, slides and thumbnails, ChatGPT Image 2.5 at low or medium is the cheaper row and costs between 17 and 38 percent of Seedream. For a final where you want the high tier, Seedream 5.0 Lite is the cheaper row at 66 percent of the price of 2.5 high. If you need to pass many references, ChatGPT Image 2.5 takes up to 16 against Seedream's 10.

Neither choice is a statement about image quality. The tiers set what you pay, and your own side-by-side tells you whether medium is enough for the job.

Where the crossover moves

Because 2.5 is cheaper at wide ratios, the point where it overtakes Seedream shifts. At 16:9 the high tier costs less than it does at 1:1, which pushes the crossover closer to the high tier; at 1:1 it is firmly between medium and high. Seedream stays at $0.04375 for every ratio it lists. If you ship mostly 16:9 or 4:5 images, measure the exact number with the endpoint call at the end of this post rather than reusing the 1:1 table.

Monthly budget view

Take 2,000 images a month. At 1:1 that is $33.00 on 2.5 medium, $87.50 on Seedream 5.0 Lite and $131.75 on 2.5 high. Moving the same volume from high to medium saves $98.75 a month, which is a bigger lever than switching model. If most of your images are drafts that never ship, the cheap tiers do the heavy lifting and a per-image flat price looks expensive by comparison.

If instead nearly every image is a final, the flat Seedream price is simpler to forecast, because it does not move with ratio or tier. Pick the rows by how much of your volume is draft and how much is final, not by the headline price alone.

Check your own number

Ask the endpoint for your model and read the billable lines. The record's pricing[].cost_usd is the billed amount, so no multiplier is needed. Compare it with Seedream's single line.

for m in openai/gpt-image-2.5 bytedance-seed/seedream-5-lite; do
  curl -s "https://api.sume.com/v1/images/models/$m/endpoints" \
    -H "Authorization: Bearer $SUME_API_KEY" \
    | jq -c '.endpoints[0].pricing'
done