500 papers ! There is a trick. There can be many authors in one paper. Professors can use their assistants and students to do the research and write papers. The real author is typically a PhD student who has done the work. The professor has of course supervised not one student but many.
Professors have connections to other professors and they co-author their results.
Of course you divide your research into many publications. Each of them contains a tiny part of the results of one research group.
Requiring a large number of papers effectively blocks the entry of outsiders to academia. Without research groups and connections, mass production of papers is not possible.