4chan (and its users) probably want a fast downlink. The author touts a cheaper provider, but the service they are receiving is an order or more of magnitude slower service from my anecdotal test through wget(s) of images on both OP's and 4chan's sites. That is, a pair of dedicated and unmanaged servers is not, AT ALL, comparable to a CDN's offerings.

4chan probably also expects to have more than an email (and timely) endpoint with which to correspond with the provider of their most core site-service -- image serving.

4chan is an enterprise customer. They pay the $3000/mo.

They're not hosted at CloudFlare. CF is basically a caching reverse proxy.

I'd bet they pay, and it makes for great PR too. "We can handle 4chan, we can handle your site!"

Because moot wants 4chan to actually be online occasionally, and to load in a reasonable amount of time. Notice how terrible pr0gramm.com performs, with a tiny fraction of the traffic 4chan gets. That's why real sites can't just get phoney "unlimited bandwidth for $20/month".