I can't speak for paying markets for short stories, since I don't write short stories. For poetry zines, few are able to pay to begin with. Outside of journals that can rely on institutional funding or a paying subscriber base, the ones that do pay often charge submission fees. The thought has crossed my mind that getting paid $20 or whatever is nice, but if they charge to submit ... isn't that just going to be a small piece of the $$$ coming in from all of the people they rejected? Nothing inherently nefarious about that, but for $20 for a poem, it can seem a little ... grasping? Why bother?