In AWS Cost Management, when we group costs by "Instance Type" for RDS Service I can see the No Instance Type *** is getting a really large portion of the total cost. In my case, it's around 45%.
At the bottom of the page we can see an explanation:
***This category includes costs (e.g., data transfer in/out) that are not directly attributable to a specific Instance Type.
What can be part of that except data transfer? Provisioned IOPS maybe?