@nprofile1q... in Singapore we have something similar called Carousell, which seems to be pretty much the same thing.
In my profile I have clearly stated that I don't engage in haggling, but every. single. time they ask 'what's your best price?' or just outright make an offer at half the listed price. Add to this that I usually sell my stuff really cheap.
Apologies for stealing your soap box, but this is an important topic.