Balance for 50 Grok 15-second clips: about $9.50, or a 402

Fifty 15-second clips on grok-imagine-video-1.5 cost about $9.50 on Sume: 15 seconds is $0.1875 at $0.0125 a second, which ceils to $0.19 a job, and 50 x $0.19 is $9.50 (the unrounded sum is $9.375). If the wallet is short, a submit fails with 402 insufficient_credits before any provider work starts.

Why the balance must cover the whole wave

Sume reserves a job's credits at submit and releases the reservation if the job fails. The docs describe the 402 as "workspace balance below the reserve". So the balance you need is not only the total of the clips that have finished, it is the total of everything you have submitted and not yet settled. A loop that fires all fifty at once needs the full amount available at the moment of the last submit.

What to do on a 402

Check the balance before the loop, submit in waves, and stop the loop on a 402 instead of retrying it. Retrying a 402 in a tight loop only burns requests. Top up, then restart the loop with the same Idempotency-Key values so the jobs that already exist are returned, not billed again.

Jobs that sit in the queue are normal. Workspace concurrency limits apply when workers pick jobs up, not when the API accepts valid jobs, so queuing fifty clips does not mean fifty run at once.

• Do not resubmit the same request without the same Idempotency-Key; a replay with a different body returns 409.
• Do not treat a queued job as stuck; poll GET /v1/jobs/{id}/status with backoff.
• A failed job releases its reservation where applicable, so the reserved amount is not lost.