Data storage has become so cheap that we don’t worry about how junk we are storing… until we get the first AWS bill with the spikes in data transfer.
As a rule of thumb: it is like a flight ticket, the longest the distance, the most expensive is the transfer.
Moving data from AWS to the Internet is more expensive than moving data between regions. Moving data between regions is more expensive than moving data between availability zones.
The good news is that you are not being double charged: only the data moving out is being charged, not the data you are receiving at the other end.
Cloudability has a great guide about this.