This may be arguably nitpicking, but the following statement from TFA isn’t exactly the case:

> Moreover, uploading to S3 - in any storage class - is also free!

Depending upon how much data you’re transferring in terms of storage class, number of API calls your software makes to do so, and the capacity used, you may incur charges. This is very easy to inadvertently do when uploading large volumes of archival data directly to the S3 Glacier tiers. You absolutely will pay if you end up using millions of API calls to upload tens of millions of objects comprising tens of terabytes or more.