While I was digging up an additional link, it appears Cloudflare R2 allows no egress fees.
https://www.cloudflare.com/developer-platform/r2/
10GB free to host, no egress fees.
Combined with a cloudflare worker, it seems reasonable that the object storage could be managed.
In this case you’re already paying for storage so egress is free.
A 10 gig fibre connection is another way to start.
The internet always costs someone.
This works well only if many of the watchers have significant upload bandwidth and aren't behind firewalls that prevent them from outputting blocks of video.
This is different from torrent-type systems or Usenet, which distribute persistent copies. With Peertube, only the original server permanently hosts the video. Everybody else is just caching. So the disk usage of watchers isn't that big.
It's all done in the browser.