The editors of good journals (APS Physical Review Letters for instance) provide significant service and it is reasonable to pay for it: from simple things like

The editors of good journals (APS Physical Review Letters for instance) provide significant service and it is reasonable to pay for it: from simple things like significantly improving the quality of the prose and typesetting to more crucial stuff like properly moderating the review process (picking appropriate reviewers, controlling for conflict of interest, filtering out superfluous submissions).