It is interesting to see that they could move 76.8GB of data in 1 hour per-instance with the old architecture, while I can move 120GB of data in 1 hour locally between 2 laptops over wifi.
An additional issue is that the same interface is used for serving the data out to the cache customers as is used for fetching from S3, (serving hundreds of gigs to hundreds/thousands of clients from ram) which is something your laptop also probably isn't doing.
S3 is big and reliable. It isn't fast or cheap.