I like to think of myself as a reasonable person. Before I sell things I meticulously go over my items, I check comps for either the same item and size or something similar, and I'm open to *reasonable* offers.
Now, what I consider reasonable is about 20% off the listing price. The vintage pieces on Poshmark right now have already been marked down 20%+ their original price. So no, I'm not really inclined to mark them down a further 20-30%. New listings however I am more flexible on (especially when bundling!). I know everyone is out for a deal but it's outright insulting sometimes when you consider how much I paid (full price), that many of these are in better condition than when I bought them, and that I go over each and every item and explicitly state any and all things that may be considered a defect.