Why a seven-second clip costs more
Tiered models sell duration in whole steps, so seven seconds buys the ten-second price. How to write scene lengths that land inside a band instead of past it.
On Hailuo 2.3 Fast a six-second clip is 14 credits and a seven-second clip is 28. Not 16, not 17. Twenty-eight, because the model sells two durations — up to 6s and up to 10s — and seven seconds does not fit in the first one.
That is a doubling for one second of ambition, and it is entirely avoidable at the script stage. It is also not a quirk of one model. Three separate billing shapes in the catalog round duration upwards, and each one rounds differently, which is why "keep clips short" is bad advice and "land on a step" is good advice.
Three staircases, side by side
| Billing shape | Model | 3s | 5s | 6s | 7s | 10s |
|---|---|---|---|---|---|---|
| Duration tiers (6s / 10s) | Hailuo 2.3 Fast | 14 | 14 | 14 | 28 | 28 |
| Five-second blocks | Seedance 1 Pro Fast | 62 | 62 | 124 | 124 | 124 |
| Base block + marginal seconds | Kling O3 Pro Image to Video | 70 | 70 | 84 | 98 | 140 |
Read across each row and the difference in behaviour is obvious.
Hailuo 2.3 Fast is a two-step staircase. It publishes exactly two durations, so everything at or under six seconds costs 14 and everything from seven to ten costs 28. The whole family shares that shape: Hailuo 2.3 Standard is 28 and 56, Hailuo 2.3 Pro is 49 and 98. Every one of them doubles between the two steps. One caveat worth stating plainly: the Fast tier is currently discounted, so the figures above are the live prices, not the full rate. When a discount lands or lapses the entire staircase moves with it, which is why the model page is the number to trust rather than a blog table.
Seedance 1 Pro Fast bills in whole five-second blocks at 62 credits each, and it sells 5s and 10s. So the sixth second costs 62 credits and the seventh, eighth, ninth and tenth add nothing on top. That is the same staircase logic with an endless run of steps rather than two.
Kling O3 Pro Image to Video is the third shape: 70 credits buys the first five seconds as one indivisible block, then each additional second is 14. It rounds only at the bottom. A three-second clip costs exactly what five costs, and after that the meter is continuous — so this family punishes short clips rather than long ones.
Why seven is the worst number in the catalog
Effective cost per second is what makes the point land. On the tiered model, six seconds works out to about 2.3 credits a second. Seven seconds works out to 4. It is the single worst value in the whole duration range, and it is one second away from the best.
The sawtooth is the entire story of block pricing. Between steps, extra length adds nothing — the ninth second on a tiered model costs no more than the eighth, and neither does the tenth. At a step, one second costs as much as the previous six. So the optimisation is not "make it shorter". It is "make it land exactly on a step", and shorter is only better when it moves you down a step.
This also inverts the usual instinct about trimming. Trimming refunds nothing: you are charged for the duration you generated, not the footage you kept. A ten-second render cut down to seven in the edit costs the same as a ten-second render you used in full. The decision has to happen before the render, in the shot list.
Two short clips beat one long take
Here is the finding that changes how you write scenes, and it falls straight out of the table.
On Hailuo 2.3 Fast, two six-second clips cost 28 credits — exactly the same as one ten-second clip. Same spend, twelve seconds of footage instead of ten, and a cut point in the middle that you would probably have wanted anyway. The single ten-second take gives you fewer usable seconds and no edit.
The same holds on the block model. Two five-second renders on Seedance 1 Pro Fast is 124 credits; one ten-second render is also 124. Two shots, two framings, two chances for one of them to land, for the price of one long take that has to work end to end.
That is not an argument for never generating long clips. A continuous camera move, a single unbroken performance, a shot where the cut would be visible — those need the length. It is an argument that when you are writing "roughly ten seconds of the product on a table", you are choosing between one ten-second attempt and two six-second attempts at the same price, and the second option is usually the better bet.
Writing scene lengths that land inside a band
The practical version is a shot-list habit rather than a pricing trick. Write durations that name a tier, not a feeling.
| What the brief says | What to generate | On Hailuo 2.3 Fast |
|---|---|---|
| "about 5 seconds" | The 6s tier, and use all of it | 14 credits, nothing wasted |
| "about 7 seconds" | Rewrite the beat to fit 6s | 14 credits instead of 28 |
| "about 8 seconds, needs a cut anyway" | Two 6s beats | 28 credits, 12 usable seconds |
| "one continuous 8-second move" | The 10s tier, trim to 8 | 28 credits, 2 seconds discarded knowingly |
| "12 seconds of ambience" | Two 6s clips, cross-cut | 28 credits |
Four rules cover most of it:
- Look up the model's published durations before you write the shot list. Some models sell two lengths, some sell every whole second from three to fifteen. That single fact decides whether you are writing to a staircase or to a meter.
- Round your beats down to the tier, not up. A six-second beat that wants seven is a directing problem you can solve without spending a credit. A seven-second beat that genuinely has to be seven is a 2× decision, and worth making deliberately rather than by accident.
- Prefer two shots to one long one when the price is equal. You get a cut, a second framing, and insurance against one of them failing.
- Check the model page rather than a remembered number. Tier prices move when a discount lands, and the whole staircase moves together.
For the full arithmetic on both shapes, what a seven-second clip costs on a tiered model covers the rounding, and what a clip longer than five seconds costs covers the base-plus-marginal family where the floor is the trap instead of the ceiling.
FAQ
Can I generate exactly seven seconds?
Only on a model that publishes seven seconds as a duration. Tiered models sell the lengths they list and nothing in between, so a seven-second requirement is rendered at the next tier up, billed at that tier, and trimmed afterwards. Models that meter every second individually will give you seven and bill you for seven.
Do I get anything back for the seconds I trim off?
No. The charge is for the duration you generated. Trimming is an editing step downstream of a completed render, and the render was already paid for at the length you asked for. This is why the length decision belongs in the shot list rather than the timeline.
Is tiered billing worse than per-second billing?
Not inherently. Used fully, a tier is very competitive — six seconds at 14 credits is cheap footage. Overshoot it by one second and it is the worst value available. Tiered billing rewards planning and punishes drift, where per-second billing is indifferent to both.
Does resolution change the tier price?
Not on the tiered models above — the tier is a duration price and it is the only thing the matrix reads. Models where resolution switches the rate are a separate billing shape entirely, and on those the resolution band multiplies every second rather than stepping the total.