Forty 2K thumbnails: Nano Banana 2.1 $6.00 or Nano Banana Pro $7.50

A set of 40 thumbnails at 2K costs $6.00 on Nano Banana 2.1 ($0.15 each) and $7.50 on Nano Banana Pro ($0.1875 each), a gap of $1.50. At 4K the gap widens to $7.00.

Pro is flat at $0.1875 per image from 0.5K through 2K on Sume and doubles at 4K, while 2.1 rises by tier, so 2.1 is the cheaper model at every tier but the gap is smallest at 2K.

The 40-image bill

Per image from the price tool; 40 images is 40 x the per-image price. The last column is the extra you pay for Pro on 40 images.

How to decide

Run the same five prompts on both at the tier you will ship, and compare text rendering and character consistency, the two areas where Google's changelog says Nano Banana 2.1 improved (read 2026-10-09: better prompt adherence, multi-turn character consistency and text rendering). If 2.1 passes, the Pro premium on 40 images is pure margin you keep.

A mixed plan also works: generate 40 at 2.1 and re-render only the few that fail on Pro. Re-rendering 6 of 40 on Pro adds $1.125 at 2K.

curl -X POST https://api.sume.com/v1/images \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: thumb-batch-07-img-12" \
  -d '{"model":"google/nano-banana-2.1","prompt":"YouTube thumbnail, surprised host, bold shapes","resolution":"2K"}'

Gotchas

• Check the model's accepted resolution values in the image model endpoints before you send a tier.
• Nano Banana 2.1 adds the aspect ratios 1:4, 4:1, 1:8 and 8:1 at 1K, 2K and 4K, which suits banners, not 16:9 thumbnails.
• Image jobs reserve the price at submit like video jobs, so 40 queued images need $6.00 free balance on 2.1.