Cloud pricing term
What is inter-region transfer?
Inter-region transfer is traffic that crosses from one cloud region to another.
The expensive mistake
Using the public-internet egress rate for replication, backups, or failover traffic between regions. Providers price region pairs differently, and the charged side can differ. A low-cost standby can be overwhelmed by the recurring transfer needed to keep it current.
Where it appears on your bill
Look for source-region data-transfer-out lines, inter-region egress, replication transfer, or destination-pair usage types.
Worked example
Google Cloud lists $0.02/GiB for many North America-to-North America inter-region paths. At 100 GiB, 100 x $0.02 = $2.00. Added to the dated example's $6.114792 e2-micro compute figure, the known subtotal becomes $8.114792 before disk and public IPv4.
Example prices checked: