As far as I know, there is no cost to use the scheduler. I've been using it on my site to run a daily task.
The scheduler launches a URL at a defined interval. You can set up a WebAPI method to be called by the scheduler. Your WebAPI method should run whatever task you need to run.
Unfortunately, there isn't a lot of documentation regarding the setup and configuration. If you have problems, submit a support ticket. The support team is very good.