> In Netflix' case, this doesn't even count their vast replicated CDN infrastructure between your device and S3. There is part of your answer. They only pay S3

> In Netflix' case, this doesn't even count their vast replicated CDN infrastructure between your device and S3. There is part of your answer. They only pay S3 outbound on cache misses, not on cache hits. That will lower their S3 bandwidth bill to 1/50th or 1/100th of the full cost. Also, Netflix doesn't pay list prices for AWS, and they made a call that they wanted to be fully cloud based early in the streaming service's life. Maybe they would do it differently today, but that ship has obviously sailed for them. On the other hand, lots of large AWS hosted services do discover that they need to move off in order to get their costs right; I have quite a bit of first hand experience there. > Glacier Costs and time to retrieve data from Glacier are quite different, and I would only use it for data that I basically never expect to access. A service like Backblaze couldn't use Glacier in reality, despite being a service for backups. > Bargain basement drive arrays On the contrary, I think that building it yourself with basic hardware building blocks is much more common at large scale Internet companies. A less technical or more appliance driven company might choose NetApp or EMC, but I don't think it's the right move for somewhere with some in-house expertise. It's the right move if you want more of a black box that you hope will work without much internal effort (hint: it won't work out that way).