[dalai]

I used to be an editor in a journal from one of the big publishers (not Elsevier). We searched for reviewers, invited them, reminded them when they were late in responding, evaluated their submissions, send the approvals, etc. And I didn’t get paid a dime. All the publisher had to do was maintain the platform. And sure that costs money too, but the costs are shared between multiple journals and papers.

[YuriNiyazov]

Yea, that's not a good model. Better publishers have publishing managers, internal employees assigned to work with editors to get this done.

From https://www.mdpi.com/editors "MDPI is headquartered in Basel, Switzerland. The in-house staff consists of Managing Editors, Assistant Editors, Production Editors, English Editors, Copyeditors, Data Specialists, Software Engineers and Administrative Specialists. Except for most English Editors, all are employed by MDPI and its subsidiaries and work at the MDPI offices. Our collaborating editors on our Editorial Boards are typically employed at academic institutions or corporate research facilities located all over the world.

...

Assistant Editors process manuscripts through the peer-review and production procedures..."

[justeleblanc]

They're just people running the peer review and production systems (think the online submission system, solving technical issues, writing emails, etc). It's in the name: assistant. They're not the people looking for peer reviewers or doing anything scientific.