I sold a fair amount on FB Marketplace and have gotten low-ballers. I've had a few people haggle in person but I say the price is firm. It does depend how desperate you want to sell something. Like I would look at how much it costs new, halve it, and maybe lower it. Or check similar listings. But if I'm desperate to sell it quickly, I'll price it lower. I also try to be more self-conscience about my spending. It's a pain to sell things on the used market especially with hyperinflation.
I've sold/bought probably 75-90 items in my FB marketplace spaces. I have not had one bad interaction with haggling
in person. I get all that out of the way in the messaging. I've had a few people say "no" when something was, lets say, 100 bucks and I said 80 bucks (thinking I could meet at 90) and not then going any further.
I usually just pay asking price, but if something is not worth what they are asking even at a lower price, I'm going to see if they will go lower.
One reason I feel I've had success on Marketplace is because I don't sell clothes...

That kind of stuff would frustrate me. People coming over, trying stuff on and then not taking it? nah.