# How per-second pricing works for realtime video, with worked examples

> Understand ready-second video API billing, compare model rates and estimate session costs. Queueing and startup are free; release sessions to stop billing.

Source: https://windflow.online/guides/how-per-second-pricing-works · Updated 2026-10-11 · Windflow Labs

Windflow bills realtime video by the **ready session-second**: one second during which a session is ready and returning frames. Rates run from **$0.0017 to $0.0069 per second** depending on the model, which is $6.12 to $25.00 per hour of ready time. There is no subscription, no seat fee and no minimum.

This guide shows what is and is not metered, what a session costs on each model, and how to estimate a product's bill before you build it.

## The price table

Current public rates, in US dollars. They are indicative private-beta rates and are also exposed at `GET /v1/pricing`.

| Model | Per second | Per minute | Per hour | A 10-minute session |
|---|---|---|---|---|
| [Helios](https://windflow.online/models/helios) | $0.0017 | $0.102 | $6.12 | $1.02 |
| [SANA-Streaming](https://windflow.online/models/sana-streaming) | $0.0019 | $0.114 | $6.84 | $1.14 |
| [LongLive-2.0](https://windflow.online/models/longlive-2) | $0.0021 | $0.126 | $7.56 | $1.26 |
| [JoyAI-Video-Edit](https://windflow.online/models/joyai-video-edit) | $0.0021 | $0.126 | $7.56 | $1.26 |
| [DreamX-World-5B](https://windflow.online/models/dreamx-world-5b) | $0.0023 | $0.138 | $8.28 | $1.38 |
| [ABot-World-0-5B](https://windflow.online/models/abot-world-0-5b) | $0.0023 | $0.138 | $8.28 | $1.38 |
| [LingBot-World 2.0](https://windflow.online/models/lingbot) | $0.0024 | $0.144 | $8.64 | $1.44 |
| [Matrix-Game 2.0](https://windflow.online/models/matrix-game-2) | $0.0024 | $0.144 | $8.64 | $1.44 |
| [LTX-2.5](https://windflow.online/models/ltx-2-5) | $0.0040 | $0.240 | $14.40 | $2.40 |
| [MiniMax FastH3](https://windflow.online/models/fast-h3) | $0.0069 | $0.417 | $25.00 | $4.17 |

Eight of the ten models sit between $0.0017 and $0.0024 per second. LTX-2.5 and MiniMax FastH3 cost more because they are larger audio-and-video models that need more GPU to stay interactive; the other eight are video-only.

## What counts as ready time

The meter starts when a session enters **ready** and stops when it is released or ends.

- **Not billed:** time in the queue, worker startup, and the documented reconnect grace.
- **Billed:** every ready second, including seconds when nobody is watching the stream.
- **Pausing the video does not stop the meter.** Pausing a track only stops delivery to that connection, and a paused generation can still hold the GPU. Release the session when the experience is finished or idle.
- **Extra viewers are free.** One session is metered once, however many authorised guests receive it. Separate concurrent sessions each carry their own meter.

## Why the rates differ

Rates follow the GPU and runtime profile a model needs to stay interactive, not an abstract unit such as pixels or output seconds. A 5-billion-parameter world model and a 35-billion-parameter audio-video model do not occupy the same hardware, so they do not cost the same per second.

## Estimating a product's cost

Cost is sessions times seconds times rate. Two worked examples:

- **A demo on a landing page.** 200 visitors each run a 3-minute Helios session: 200 × 180 s × $0.0017 = **$61.20**.
- **A creative tool.** 20 creators each steer LingBot-World 2.0 for 2 hours a day: 20 × 7,200 s × $0.0024 = **$345.60 per day**.

Two habits keep the number honest. Count only the seconds a session is actually ready, and multiply by peak concurrency when you size the account, because every concurrent session is metered separately.

## What a $5 grant buys

Approved accounts start with $5 and four concurrent sessions. At the published rates that is about 49 minutes of Helios, 21 minutes of LTX-2.5 or 12 minutes of MiniMax FastH3. It is enough to evaluate several models for real, not just read about them.

## Why you may see a 402 with a positive balance

Creating a session reserves the model's rate multiplied by its maximum session length. Concurrent reservations reduce the balance you can spend. When a session ends, the actual ready seconds settle and the unused part of the reservation returns to your balance.

## How to keep the bill down

1. **Release sessions the moment a user leaves.** An idle ready session still bills until it hits the model's session ceiling.
2. **Prototype on the cheaper models.** Helios, SANA-Streaming and the world models cost under $0.0025 per second; move to LTX-2.5 or FastH3 when you need generated audio.
3. **Share one session.** A broadcast to many viewers is one meter, not many.
4. **Cap session length per user.** Short-lived, scoped tokens can carry a session budget, so the worst case a user can spend is known before the token leaves your server.

## Renting a GPU versus paying per session

Renting a GPU bills the whole hour whether or not anyone is using it, and leaves you to build the streaming layer, the session state and the scheduling. Per-session billing charges only ready seconds and includes those parts. For steady, round-the-clock load on one model, dedicated capacity can be the better fit; Windflow scopes that separately as reserved scale. For spiky, interactive or early-stage traffic, per-second billing keeps cost proportional to use.

## FAQ

### What is the cheapest way to run a realtime video model without managing GPUs?

Pay per ready session-second on a hosted platform. On Windflow the lowest rate is $0.0017 per second (Helios), which is $6.12 for an hour of ready time, with no GPU to provision and no charge while a session is queued or starting.

### Is there a free trial?

Approved accounts start with $5 of usable balance across the public models.

### Are recordings and uploads billed separately?

During private beta the published ready-session rate is the meter. Temporary recordings expire after 24 hours; high-volume exports, dedicated storage and private delivery are scoped separately.

### Where can I see current rates?

On the [pricing page](https://windflow.online/pricing), in each model's page, and at `GET /v1/pricing`.