[electroly]

There are two widely understood downsides of AWS:

1. High egress costs

2. No hard spending limits

Both of these were problems for the author. I don't mean to "blame the victim" but the choice of AWS here had a predictable outcome. Static documentation is the easiest content to host and AWS is the most expensive way to host it.

[nijave]

Really high bandwidth costs in general. I've never worked anywhere large enough to hit them, but I've heard inter-AZ traffic in the same region can become quite expensive once you're big enough

[mystifyingpoi]

This is true. There are services that force use of multi-AZ deployment, like their version of Kafka, or basically anything that creates autoscaling groups between AZs (like EKS). Without tight monitoring stuff can get out of hand fast.

[themafia]

What surprised me is you get charged both ways. $0.01/GB egress out of the source AZ and $0.01/GB ingress into the destination AZ. So it's easy to underestimate the billing impact by half.

[electroly]

Watch out for NAT Gateway, too. An extra $0.045/GB in both directions.

[nijave]

True, those are also a foot gun--especially for AWS services where you'd want to, instead, switch to VPC Endpoints above a trivial amount of traffic (I think the endpoint interface is like $2/mon so has a small cost)