Synthesia Assistant adds B-roll free: the itemized Sume way

Synthesia's updates page says its Assistant now adds curated AI B-roll at no extra cost, announced September 15, 2026. Sume works the other way: each asset is its own priced job. You pay for the avatar clip per second, for any B-roll you generate with the model you choose, and for the composition step, and nothing is hidden inside one plan.

What is priced separately in Sume

The public API price list shows the relevant line items. Timeline output is $0.10 per output minute and timeline compose is $0.02 per job, alongside the avatar video per-second rate.

Example: a 15 second composed clip

Standard avatar video at 15 seconds is $2.76. Compose adds $0.02, and the timeline output of 15 seconds at $0.10 per minute is $0.025. B-roll generation costs depend on the model you pick, so check that model's page. The sum of the lines you see is the bill.

Included B-roll is simpler to start with. Itemized pricing is easier to cap, cache and reuse across variants.

When each approach fits

For a one-off explainer, an assistant that picks cutaways is fast. For a repeated format, such as 40 variants of one ad, you want the avatar clip rendered once and the B-roll reused. Itemized jobs let you do that without paying again for the parts that did not change.

Always check what the vendor's phrase 'no extra cost' covers on your plan, since the page does not give limits.