Balto: https://www.getbalto.com/

Repository hosting for Apt and RPM and a couple of other formats. No real customers but I do offer it to a couple notable open-source projects: Helm for their unofficial Apt package (which I personally maintain) which gets 200,000+ downloads/month and Authelia (15k Github stars). The biggest single cost is StackPath CDN's bandwidth (a bit more than $100/mo) so I'm planning to move to BunnyCDN soon.