Finance asks for a way to attribute VPC egress costs to application teams via billing export. Which approach gives the most accurate per-team cost breakdown with minimal infrastructure changes?

Applying labels to compute instances and using Cloud Billing export to BigQuery is the most effective method because Google Cloud billing exports include resource labels, allowing for granular cost attribution directly to the source of egress traffic (the instances). This provides an accurate per-team breakdown with minimal infrastructure changes since labels are a metadata feature. Network tags on firewall rules are for network policy enforcement, not for billing attribution. While folders can separate teams, keeping all projects under one billing account doesn't automatically break down egress costs by team; you'd still need a labeling strategy within projects or separate billing accounts. Applying labels only to VPC networks is insufficient because egress costs are primarily generated by individual instances within those networks, not the networks themselves, leading to less accurate attribution.