Egress Pricing
The asymmetric charging model in which data entering a cloud is free and data leaving is billed, shaping architecture more than compute pricing does.
Inbound transfer is generally free; outbound is charged, and the rate varies by destination — to the internet, to another region, to another availability zone, or to a peered network.
The architectural consequences are larger than the headline compute prices most comparisons focus on:
Cross-zone traffic is charged in both directions in some providers, which makes zone-aware routing a cost control as well as a latency one. A service mesh's locality-aware load balancing frequently pays for itself here.
Chatty microservices are expensive when they cross zones. A design that looks clean can produce a substantial transfer bill from nothing but internal calls.
Private endpoints are usually cheaper than NAT for reaching managed services, because NAT charges per gigabyte processed and a private endpoint charges an hourly rate.
CDN offload reduces origin egress, and is often justified on transfer cost alone before any latency argument.
Multi-region replication has a per-gigabyte cost that grows with data volume, and it is a recurring charge rather than a one-off.
The strategic point: egress is what makes data gravity real. It is priced to make moving large volumes out unattractive, which is the mechanism behind most cloud lock-in.