In AWS Transit Gateway you are charged for the number of connections that you make to the Transit Gateway per hour and the amount of traffic that flows through AWS Transit Gateway. You can create a Transit Gateway to connect to multiple Amazon Virtual Private Clouds (Amazon VPCs), Direct Connect and VPNs, and that Transit Gateway can work across accounts. The VPC account owner is billed hourly for each hour that their Amazon VPCs attached to an AWS Transit Gateway.
For AWS VPN attachment, the Transit Gateway owner is billed hourly for VPN attachments. For AWS Direct Connect attachment, the Direct Connect Gateway owner is billed hourly for Direct Connect attachment. For peering attachments, each Transit Gateway owner is billed hourly for the peering attachment with the other Transit Gateway.
Hourly billing will also start when the Transit Gateway owner accepts your VPC and it stops when the attachment is deleted. Each partial VPC Transit Gateway hour consumed is billed as a full hour. Similarly, a VPN attachment will be charged hourly.
AWS Site-to-Site VPN connection pricing still applies in addition to AWS Transit Gateway VPN attachment pricing. Please see the product page for AWS Site-to-Site VPN pricing.
Data processing charges apply for each gigabyte sent from a VPC, Direct Connect or VPN to the AWS Transit Gateway. Data processing charges also apply for each gigabyte received by each instance received by a multicast receiver. Data processing charges do not apply for data sent from a peering attachment to a Transit Gateway. Data transferred over a peering attachment incurs the standard inter-region data transfer charges as explained in the EC2 on-demand pricing page.
You created an AWS Transit Gateway in US East (Ohio) and attached an Amazon VPC to it. You created a route to send traffic to another VPC via the Transit Gateway. 1 GB of data was sent from an EC2 instance in that VPC to another VPC.
AWS Transit Gateway hourly charge: You will be charged for your AWS Transit Gateway on an hourly basis. For this region, the rate is $0.1 per hour ($0.05 per VPC attachment). When a Transit Gateway is shared across different AWS accounts, the hourly fee is charged to the account owner of the VPC attached to the Transit Gateway.
Transit Gateway data processing charge: 1 GB was sent from an EC2 instance in a VPC attached to Transit Gateway. The Transit Gateway Data Processing will result in a charge of $0.02. Data Processing is charged to the VPC owner who sends the traffic to Transit Gateway.
Transit Gateway data processing charge across peering attachments: 1 GB was sent from an EC2 instance #1 in a VPC attached to Transit Gateway #1 (N. Virginia region) over a peering attachment to Transit Gateway #2 (Oregon region), where it will reach EC2 instance #2 within a VPC. The total traffic related charges will result in a charge of $0.04. This charge comprises $0.02 for Transit Gateway Data Processing on Transit Gateway #1 along with $0.02 for outbound inter-region data transfer charges. Here Transit Gateway #2 will not incur data processing charges, as they do not apply for data sent from a peering attachment to a Transit Gateway. As inbound inter-region data transfer charges are free, no further charges apply to the Transit Gateway #2 (Oregon region) side.