You would replace the Fastly CDN with Storj, correct? Your link mentions 1500TB of Fastly traffic, which would cost $12k with Storj. Not sure if this is related to parent's 3TB/day number, but I went with that when I estimated the $8k.
I think the best cloud solution might be something like Storj + Fastly or Cloudflare end-to-end. But I'm really curious how much could be chopped off if you tried to solve this on-prem.