I wondered about this too, especially since their marketing makes a huge deal about how "We never charge for bandwidth" [1]. It turns out that enterprise plans

I wondered about this too, especially since their marketing makes a huge deal about how "We never charge for bandwidth" [1]. It turns out that enterprise plans don't exactly charge per-gigabyte like other CDNs, but the cost does increase based on your bandwidth usage. There aren't a ton of explicitly called out features that require an enterprise deal, but I expect a customer of any significant size will be under one (or encouraged to do so). It's the only way to get an SLA and to modify the terms of your contract with them, among other things that businesses care about. As a result of the difference in price between the plan types, I would speculate that the service is subsidized by the enterprise customers. However, the free or lower cost customers were probably essential to building their peering relationships before they had significant enterprise users, and that has a very direct relationship with their cost to serve traffic. [1] https://www.cloudflare.com/plans https://www.cloudflare.com/plans