Note that there are plenty of legitimate journals, like PLOS, that charge a fee to publish. It's a common business model for open access journals. Usually they

Note that there are plenty of legitimate journals, like PLOS, that charge a fee to publish. It's a common business model for open access journals. Usually they have some mechanism for waiving the fee if an author can't afford it. Also, allegedly many of these journals actually have per-paper expenses in the hundreds of dollars (!!), mostly from editor time spent soliciting and managing reviewers. That seems crazy. In contrast, major ML venues like NIPS handle all the review management in a mostly automated way and are run by volunteers. But then again, the average review quality at ML conferences seems to be pretty poor, at least compared to what I've heard about in some other fields.