> Nothing. You generally only pay for data going out of cloud providers. Not data going in or data being transferred within the same region. This is not true,

> Nothing. You generally only pay for data going out of cloud providers. Not data going in or data being transferred within the same region. This is not true, AWS charges for all traffic cross AZ, so if you want a resilience within a region (which you mentioned in next paragraph) you will do a lot of that talking and this ends up a non trivial cost. You can do some optimization though by having your apps being aware of AZs they are on, but most places don't do that, more common are places that run everything from a single AZ.