Some of it is on Akamai as the article describes, but if we had everything on CloudFront and wanted to estimate the cost of 1M orders: 2.38 TiB out + (say) 1 KiB/request * 67M or 67 GiB in: that's $275.50 per 1 million orders (approximately $207 out + $67 in + $1 requests cost).
If we add 1M Lambda executions, we still get $0 since that's the entire free tier. 10M Lambda calls at 50 ms each and 128 MB of RAM cost $1.8, so that's pretty much free as well.
Assuming that CloudFront caching is configured correctly, there would be very few requests to the S3 origin so their cost would be negligible.
Someone please correct me if I've got this completely wrong. Source: https://calculator.aws/ (CF: 2.38 TB + 67 GB + 67M req).