Im a big fan of Datadog's Cloud Cost management: https://www.datadoghq.com/product/cloud-cost-management/

Outside of that though, you can go to your AWS billing, filter on RDS, and slice by usage type. They make you dig, which is why I pref Datadog

If you hook up https://vantage.sh you can filter by RDS costs > Cost by Category on a Cost Report to see this.

Disclaimer: I work for Vantage.

PS. I maintain https://ec2instances.info/rds and recently added support for Aurora I/O Optimized pricing.

You can see it in cost explorer if you break down by one of the spend types. Went and checked it: group by usage type and then filter for service: RDS and you can see your io usage broken out in plain baa cost explorer.

Lovely, thank you!