[kettleballroll]

N. Usually THE AUTHOR pays the journal to publish anything. However, the professors need publications for their CV (number of published articles is a very important metric in the academic world), to acquire new funds ("give us money to do research on topic X. Look at how much we published on this related topic before, we clearly know what we're doing") or advance in their career (ASA function of the former two points). Students need publications as part of their graduation requirements (in a lot of fields, you are required to have N publications in a peer reviewed venue to get your PhD).

So in both cases, you don't make money directly from publications, but from the prestige they bring and the credibility they're associated with ("this guy must be an expert on X, because they published on the topic").