Who do you see as current AWS customers paying bills like that? My guess is that's very niche. People who expect to use petabytes of bandwidth rarely just throw things on AWS and eat the bills. And if they do, then it sounds like they wouldn't be moved to switch anyhow.
Not current aws customers, but a friend's company basically built out their own cdn to avoid these charges. They're something like twitch -- lots of videos, lots of viewers.
Paying a fraction (there will obviously be charges beyond the $.09) but still a fraction of aws charges would have been revolutionary for them.
I think most people in that bucket knows not to serve in bulk from AWS and so just use existing CDNs. (Or, as you say, builds their own.) A good fraction of Cloudflare's business has to be fronting things that are in AWS.
For this to be disruptive, there has to be a significant amount of business that will move from AWS to Cloudflare because of this change.
https://twitter.com/quinnypig/status/1443028078196711426
Corey compares the cost of storing 1gb of data in s3 vs r2 and serving it to the internet:
> If 1 million people download that 1GB this month, my cost with @cloudflare R2 this way rounds up to 13¢. With @awscloud S3 it’s [$53,891.16]