AWS EventBridge pricing for cron events

Question

I would like to schedule triggering my Lambda function.
AWS EventBridge allows me to do this (e.g. by creating cron based rule) but I don't understand its pricing model.
It states "All state change events published by AWS services are free" but I'm not sure if an event fired by EventBridge (generated by EventBridge rule) relates to this free one. Probably not.
If it's not free, then how 30 events per month will be billed if pricing is based on million of events.

Googling didn't help. Do you have ideas how 30 events will be billed?

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Update:
While experimenting I found that we should not pay for 30 events per months but it's not clear why. Probably less than million of events are free.

Answer 1

When you enable AWS EventBridge Rule to trigger based on a fixed rate or a Cron expression, the EventBus selection gets disabled. This means, the events from this Rule will be delivered to the default bus which is where all the events from AWS services end up. Also, if you look at one of the events delivered using the fixed rate or the cron expression, the event source is "aws.events" (which is one of the AWS services. In this case, it is the EventBridge). All events generated by AWS services fall under AWS Service events and they are free.