Transit Gateway inter-region peering cost: connecting regions the expensive way

Quick answer

Transit Gateway inter-region peering connects Transit Gateways in different regions over the AWS backbone. The cost has layers: each Transit Gateway charges about $0.05 per hour per attachment (roughly $36.50 per month) for the VPCs attached, about $0.02 per GB of data processing on traffic through it, and cross-region data transfer of roughly $0.02 per GB and up for traffic between the regions. So a byte crossing regions can be processed by two Transit Gateways plus pay cross-region transfer, stacking several per-GB fees. The takeaway: inter-region Transit Gateway traffic pays processing on both ends plus transfer, so minimize the volume that crosses regions.

Transit Gateway inter-region peering is the clean way to connect a hub-and-spoke network that spans multiple AWS regions: each region has its own Transit Gateway, and the two are peered over the AWS backbone. It is operationally elegant, but the cost stacks several per-GB fees on traffic that crosses regions, so it deserves a careful look before you route heavy traffic through it.

The fee layers

Fee	Approximate rate
VPC attachment (per TGW)	~$0.05/hr (~$36.50/mo)
Data processing (per TGW)	~$0.02/GB
Cross-region data transfer	~$0.02/GB and up

Each Transit Gateway charges an hourly fee for every VPC attached to it, about $0.05 per hour or $36.50 a month per attachment. Traffic flowing through a Transit Gateway also pays a data processing fee of about $0.02 per GB. And traffic crossing between regions pays cross-region data transfer on top. The peering attachment itself connects the two Transit Gateways so their spokes can reach each other.

How a cross-region byte gets billed

Follow a byte from a VPC in one region to a VPC in another. It enters the local Transit Gateway (data processing on the source side), crosses the peering connection to the remote region (cross-region data transfer), and reaches the destination Transit Gateway (data processing on the destination side). Depending on the exact path, that byte can incur processing on both Transit Gateways plus the cross-region transfer. For a terabyte a day of inter-region traffic, the stacked per-GB fees add up quickly, potentially thousands of dollars a month.

Comparing the alternatives

Inter-region VPC peering (direct VPC-to-VPC across regions, without Transit Gateway) avoids the Transit Gateway processing fees and pays only cross-region data transfer, so for a small number of cross-region connections it is cheaper. Transit Gateway peering wins when you have many VPCs per region that all need inter-region reach, because it scales as a hub rather than a mesh, the same trade-off as the single-regionpeering versus Transit Gatewaydecision, now with cross-region transfer added on top.

Keeping inter-region cost down

The most effective lever is architectural: minimize how much traffic crosses regions at all. Keep chatty components co-located in one region, replicate only what genuinely needs to be in both regions, and compress cross-region traffic. Consolidate inter-region connectivity through the Transit Gateway peering rather than many direct links only when the VPC count justifies the processing fees. And weigh whether the multi-region design's benefit justifies its ongoing network tax, as themulti-region cost versus latency guide covers.

Because the cost depends on how much traffic crosses regions and how many attachments you run, it is best modeled at design time. Price your inter-region network against theresource catalog so the stacked processing and transfer fees are known before you route heavy traffic between regions.

FAQ

How is Transit Gateway inter-region peering priced?

Several layers: each Transit Gateway charges about $0.05 per hour per VPC attachment (roughly $36.50 a month), about $0.02 per GB of data processing on traffic through it, and cross-region data transfer of roughly $0.02 per GB and up for traffic between regions. A byte crossing regions can pay processing on both Transit Gateways plus the cross-region transfer, stacking multiple per-GB fees.

Why is inter-region Transit Gateway traffic expensive?

Because a cross-region byte can be billed multiple times: data processing on the source Transit Gateway, cross-region data transfer over the peering connection, and data processing on the destination Transit Gateway. At a terabyte a day, these stacked per-GB fees add up to potentially thousands of dollars a month, on top of the per-attachment hourly fees for the VPCs connected to each Transit Gateway.

Is inter-region VPC peering cheaper than Transit Gateway peering?

For a small number of cross-region connections, yes. Direct inter-region VPC peering avoids the Transit Gateway data processing fees and pays only cross-region data transfer. Transit Gateway peering wins when you have many VPCs per region that all need inter-region reach, because it scales as a hub rather than requiring a full mesh of peering connections, justifying its processing fees at scale.

How do I reduce inter-region networking cost?

Minimize how much traffic crosses regions in the first place: keep chatty components co-located in one region, replicate only what genuinely needs to be in both, and compress cross-region traffic. Use Transit Gateway peering rather than many direct links only when the VPC count justifies the processing fees, and weigh whether the multi-region design's benefit justifies its ongoing network tax.

When should I use Transit Gateway for multi-region networking?

When you have many VPCs in each region that all need to reach VPCs in other regions, so a full mesh of direct peering connections would be unmanageable. Transit Gateway's hub-and-spoke model needs one attachment per VPC and routes between all of them, scaling cleanly across regions via peering. For just a few cross-region links, direct VPC peering is simpler and cheaper.

How does C3X help with inter-region network cost?

C3X prices your Transit Gateway attachments, data processing, and cross-region connectivity from Terraform before you deploy, so the stacked per-GB fees are visible in the pull request. That lets you compare Transit Gateway peering against direct VPC peering for your region and VPC layout, and reconsider how much traffic crosses regions, at design time rather than after the fees compound on the bill.

What to do next

Price your inter-region network before you build it. C3X reads your Terraform and prices your resources against a live catalog. Start with the quickstart.