There's really no set answer to this. It depends on how motivated the seller is to get rid of the item, and how motivated the buyer is to pick up the item.
For me, If I want the item fairly badly, and the price is reasonable, I'll pay whatever the seller asks. If it's one of those things I think its nice to have, but not necessary, I'll ask for 25% less than the listed price.
However, whenever I sell an item, I'll always list a bit high, with the expectation that someone will bargain, although every now and then I get my listed price. But then again, I'm Chinese
P.S. If I feel I'm being low-balled on an item I'm selling, I'll ignore it. No skin off my back. Although I don't think I've ever been offered "Dank" weed before lol.