It's free to use but we add a watermark. It costs $2 to remove the watermark for a single video, $10 for a monthly subscription for unlimited videos without watermarks. But actually you can also remove the watermark for free too. We wrote an interesting post about that here: https://www.kapwing.com/blog/skipping-our-paywall-with-an-ap...

As for the CPU usage - it is quite intensive so we set up a Linode instance dedicated to processing the videos. It costs us $80 a month, but Linode throttles it automatically. That's nice because if a lot of videos are being created, it just means that they get created slower for everyone. But they don't fail.