Real publishers make a good chunk of their profits from selling subscriptions of their journals to libraries. These allow anyone at a university to read the journal, but the fee can be many thousands per year (per university). These are legitimate businesses, problems aside.

Fake ones like this make it off the $800 publishing fee. Since it's "open access" they just put the PDF online and call it a day. $800 isn't bad for a few hours of proofreading and updating one web page.