7-second 720p AI video clip: Luma lists 5 or 10 seconds, Sume bills 7

A 7-second 720p clip costs $0.63 on LTX-2.5 Fast, $0.84 on LTX-2.5 Pro, $0.56 on MiniMax-H3 at 768P and $0.525 on Sume's minimax-h3. Luma is the odd one out: its pay-as-you-go page lists Ray 3.2 totals only for 5 seconds ($0.30 at 720p) and 10 seconds ($0.90), so a 7-second clip has no listed price there, and the 10-second total is three times the 5-second one.

Why the Luma row is different

Luma prices a video by request type, resolution, dynamic range and duration, and for standard dynamic range it prints a total for each of 5 and 10 seconds. At 720p the 10-second total of $0.90 is 3.0 times the 5-second total of $0.30, not twice, and the same 3x holds at 360p ($0.06 to $0.18) and 1080p ($1.20 to $3.60). If you need 7 seconds on Luma, ask Luma which total applies before you budget, and compare the possible 5 or 10 second totals with the per-second providers: $0.30 is 4.3 cents a second at 7 seconds of use, and $0.90 would be 12.9 cents.

Duration limits on Sume

Sume's video docs give each model a valid duration range and bill linearly inside it. minimax-h3 and minimax-h3-max accept 5 to 15 seconds, wan-3.0 accepts 2 to 30 seconds, gemini-omni-flash-1.1 accepts 3 to 10 seconds, and seedance-2.5 accepts 4 to 30. A 7-second request is inside all of them. On Sume, gemini-omni-flash-1.1 at 720p would be 7 x $0.125 = $0.875, the same as wan-3.0 at 720p.

Sume reserves the estimate at submit and shows the final charge on the finished job. Use GET /v1/videos/models to read the live duration range for any model before you send an odd length.

Rounding rules to ask about

Pages that bill per second do not always say how fractional seconds round. Sume's docs say it reserves the estimated price at submit and shows the final charge on the job, so the job record is your source for the billed amount. For vendors that publish only fixed totals, ask whether a clip between two listed lengths is rounded up, refused, or billed at the shorter length, and write the answer into your budget.