Running storage system is cheaper than you think. Look at hetzner for an upper bound on how much storage costs at scale. They offer 10 TB of storage for $31/month. It mentions having "RAID-based storage" and "backups", so this presumably includes redundancy. If you can get 4 customers paying $99/year, you're already breaking even on the server. Most people probably don't have 2.5 TB worth of stuff. Backblaze only does backups, so it isn't like dropbox where you can upload whatever you want onto it. Most people don't even have computers with 1TB storage, so you'll probably be able to fit far more than 4 customers per server. Of course, this doesn't cover salaries for your engineer or marketing people, but at least it's not like moviepass where they're selling $50 worth of movie tickets for $10.