We watch the AWS Cost Explorer https://console.aws.amazon.com/cost-management/home?#/dashboard to manage our on-demand, reserved and spot costs.
AWS Cost Calculator
It would be ideal if we could plan and track costs as pseudo Costs as Code (tied to Cloud Formation/terraform scripts). There is a way to export estimates in the https://calculator.aws/#/ using https://docs.aws.amazon.com/pricing-calculator/latest/userguide/export-estimate.html
For example a T3a.small 2/2 with 20GB EBS, weekly snapshots 10Gb/month traffic out, Reserved 3years no upfront, non-convertible is $82/month