Why Services Costs in AWS and Regional Costs is different and not matching?

Example to Understand the Discrepancy:

Suppose you have the following costs:

Services Costs

Service	Cost
AWS Certificate Manager	$1,248.00
Tax	$1,543.81
Amazon Relational Database Service	$2,637.25
EC2 – Other	$2,113.58
Amazon OpenSearch Service	$1,915.42
Others	$7,523.87
Total	$16,981.93

Regional Costs

Region	Cost
Asia Pacific (Tokyo)	$18,263.64
Asia Pacific (Osaka)	$1,879.85
Global	$62.13
US West (Oregon)	$7.58
US East (N. Virginia)	$1.98
Asia Pacific (Singapore)	$0.37
Total	$20,215.55

The discrepancy between Services Costs and Regional Costs on AWS can arise due to several reasons, including:

1. Different Billing Perspectives:
   • Services Costs: These costs are calculated based on the specific AWS services you use, regardless of the region where they are deployed.
   • Regional Costs: These costs are calculated based on the AWS regions where your resources are running, and they may include additional region-specific charges such as data transfer fees or region-specific services.
2. Data Transfer Costs:
   • Regional costs might include data transfer charges between regions or within a region, which are not always itemized under specific service costs.
3. Support and Subscription Fees:
   • These may be listed separately and not directly attributed to specific regions or services, but they can impact the overall billing.
4. Taxes and Surcharges:
   • These might be applied differently based on regions or globally, affecting the total calculated costs.
5. Reserved Instances and Savings Plans:
   • The cost benefits from Reserved Instances (RIs) and Savings Plans can be distributed across multiple services and regions, making it harder to directly correlate service-specific costs with regional costs.
6. Usage and Resource Allocation:
   • Some AWS resources and services might span multiple regions (e.g., S3 storage with data replication across regions), leading to costs that are not easily attributed to a single region or service.
7. Different Billing Cycles or Periods:
   • Sometimes, discrepancies can arise if there are differences in the billing cycles or periods considered for services and regional costs.

Possible Reasons for Discrepancy:

1. Additional Adjustments: There might be additional credits, discounts, or adjustments applied to the overall bill that are not reflected in the regional costs.
2. Billing Errors or Reporting Differences: Ensure that the billing cycle or period for the provided total costs aligns with the regional costs.
3. Unaccounted Costs: There might be certain costs that are not itemized in the regional breakdown but are included in the total costs.

It’s possible that the discrepancy in the total costs is due to the disaster recovery (DR) region waivers or credits provided by AWS. If the Asia Pacific (Osaka) region is being used as a DR region for Tokyo, AWS may waive or credit the costs associated with the DR region to promote high availability and disaster recovery strategies. This could explain why the total costs are lower than the sum of the regional costs.

Scenario Breakdown:

Regional Costs Breakdown

Region	Cost
US West (Oregon)	$7.58
US East (N. Virginia)	$1.98
Global	$62.13
Asia Pacific (Tokyo)	$18,263.64
Asia Pacific (Singapore)	$0.37
Asia Pacific (Osaka)	$1,879.85

Sum of Regional Costs

7.58+1.98+62.13+18,263.64+0.37+1,879.85=20,215.557.58 + 1.98 + 62.13 + 18,263.64 + 0.37 + 1,879.85 = 20,215.557.58+1.98+62.13+18,263.64+0.37+1,879.85=20,215.55

Provided Total Costs

16,981.9216,981.9216,981.92

Identified Discrepancy

20,215.55−16,981.92=3,233.6320,215.55 – 16,981.92 = 3,233.6320,215.55−16,981.92=3,233.63

Possible Waiver for DR Region

If the entire cost of the Asia Pacific (Osaka) region ($1,879.85) is waived off, this could partially explain the discrepancy. However, this still leaves a difference:3,233.63−1,879.85=1,353.783,233.63 – 1,879.85 = 1,353.783,233.63−1,879.85=1,353.78

There might be other credits, discounts, or adjustments contributing to the remaining difference.