Comment by kordlessagain

> In a CDN, customers consume bandwidth; they do not contribute it

They contribute money which buys infrastructure.

> If Cloudflare adds 1 million free customers,

Is the free tier really customers? Regardless most of them are small that it doesn't cost cloudflare much anyways. The infrastructure is already there anyways. Its worth it to them for the good will it generates which leads to future paying customers. It probably also gives them visibility into what is good vs bad traffic.

1 million small sites could very well cost less to cloudflare than 1 big site.

I imagine every single customer is provisioned based on some peak expected typical traffic and that's what they base their capital investment in bandwidth on.

However most customers are rarely at their peak, this gives you tremendous spare capacity to use to eat DDoS attacks, assuming that the attacks are uncorrelated. This gives you huge amounts of capacity that's frequently doing nothing. Cloudflare advertise this spare capacity as "DDoS protection."

I suppose in theory it might be possible to massively optimise utilisation of your links, but that would be at the cost of DDoS protection and might not improve your margin very meaningfully, especially is customers care a lot about being online.

You're missing the economies of scale part.

OP is saying it's cheaper overall for a 10 million customer company to add infrastructure for 1 million more than it is for a 10,000 customer company to add infrastructure for 1000 more people.

If you're looking at this as a "share of the pie", it's probably not going to make sense. The industry is not zero sum.