There is a discussion on one of the issues regarding the aws data transfer: For

intra-region data transfer

, AWS calculator applies the same amount for in-bound and out-bound rates. So if you set the usage of intra-region to 1000 GB you will get:

Intra region:
(1000 GB x 0.01 USD per GB outbound) + (1000 GB x 0.01 USD per GB inbound) = 20.00 USD

But's it's probably far from reality. Do we have to split it to 2 sub-usage data for inbound and outbound or just stick to what AWS does for the sake of simplicity?

+1 on what AWS calc does, maybe we can tweak the usage file comment to say?

Monthly data transferred between availability zones in the region. Infracost multiplies this by two to account for AWS charging in-bound and out-bound rates for it.