Comment by PaulDavisThe1st

Even just the basic admin costs associated with paper review - handling that for a medium sized journal is at least one full time job - are going to add up to more than I think donations will ever generate for such a task.

My mental model is a non-print journal, so there are very few "publishing" costs, but the overall administration of things, from the tech side to the typical scientific paper processing workflow, is not a long term task for volunteers (I suspect).