High network charges forTransitGateway VPC, VpcEndpoint, TGWPeering

This is a good blog to help you: https://aws.amazon.com/blogs/architecture/overview-of-data-transfer-costs-for-common-architectures/

Are there any cross AZ charges ?

Hi, usually networking is around 10% of total bill. Since it is about 20%, I'd recommend a networking architecture review and a deep understanding of costs in Cost Explorer tool. Said that, charges have the synxtax: REGIONNAME-SERVICE-TYPE_OF_CHARGE. So:

• EUC1-TransitGateway-Bytes are the charges related to the bytes processed by the TGW on region eu-central-1,
• EUC1-VpcEndpoint-Hours are the charges in eu-central-1 for the hours that you are utilizing the VPC endpoint, and
• EUC1-VpcEndpoint-Bytes the charges for the processed bytes by the VPC endpoint on eu-central-1

Consider checking if all the traffic that flows through TGW peering could follow another path. Also, consider if a TGW is needed or not answering these questions:

1. Do you need transitive routing?
2. Is your scenario complex (10s of VPCs to interconnect and/or hybrid connectivity)?
3. Do you need high scalability because a high network growth is expected?

If you answer is no to all of them, you could consider a rearchitecture of the topology.