S3 Egress Fees: Why Downloading Your Own Data Costs So Much
Cross-posted from the Runsite blog . You put a few hundred gigabytes of images on object storage, glance at the pricing page, and the numbers look friendly: storage is a couple of dollars a month, basically a rounding error. Then the first real invoice arrives and it's a hundred and something. Nothing about how much you're storing changed. The line that blew up isn't storage at all. It's egress — the charge for data leaving the bucket — and it's the part of the bill nobody shops on. Why the storage bill blows up after the first invoice The pricing page wasn't lying to you. Object storage genuinely is cheap to sit on. On AWS S3 , standard storage runs about $0.023 per GB per month at the time of writing, so a hundred gigabytes of assets costs you around two dollars and change to keep. That's the number you compare when you're choosing where to put your files. The number you don't compare is egress: the fee for moving data out of the provider's network. It doesn't show up when you upload, and it doesn't show up while the files just sit there. It shows up every time someone downloads something — roughly $0.09 per GB to the internet once you're past a small free allowance (about the first 100 GB a month on AWS). Individually those are tiny fractions of a cent. The trouble is you're not billed once. You're billed per download, and a popular file gets downloaded a lot. Where egress hides Egress is data transfer out: every byte that leaves the provider's network. The reason it surprises people is that it isn't a single line you can point at. It's a multiplier that quietly attaches itself to things you'd never think of as "downloading": Serving assets to users. Every image, video, PDF, or download your app hands to a visitor is egress. One 4 MB hero image on a page that gets a million views a month is four terabytes of transfer out, from a single file. CDN origin pulls. Putting a CDN in front of your bucket helps, but it isn't free. Every cache miss means the CDN fetches th