OVH's download is cheaper but Backblaze is $0.005/gb/month so unless you're doing a lot of downloading, it's lower cost than OVH.
Idd, I'm building a social media service with it. So traffic is more important than storage. For long therm storage with almost no access/traffic this would be better.
Hubic by ovh is 5€ for 10TB, which would be 0.0005 €/GB/month. But i have no idea how compareable that offer is regarding features or sla. https://hubic.com/en/