Not this forum, but olx.
Had posted a FS for my 2015 MBA that had 600+ battery cycle but very good condition overall. I was optimistically expecting close to 35k having gauged price across various placesz but was willing to accept around 30k if the offer and person was genuine.
If there were 10 offers I received, 8 were close to 20k or under!
I maintain a simple thing - if seller mentions price is firm, and you are not satisfied with that price, move on, look for another stuff elsewhere. Do not bother until and unless you want it that price, and maybe if you're courteous and good enough, the seller could take off 2-5% at the time of dealing.
Coming back to the MBA, a buyer offered 32k and was willing to come at my office, check the entire stuff, if satisfied would buy at that price. It was a comfort I embrace and would be willing to take a marginally lower price.
Dude was nice, a 1st year grad who needed a MacBook for online classes and other stuffs, he was upgrading from a 2012 model.
Now that's a place most of us have been through, and when he was handing over the cash to me, I took 30k from him and both of us were satisfied with the deal.
There would be a hundred similar tales I've witnessed over the past decade across various platforms, however, the ones with the lowballs are peculiarly sick!
If I expect 30k firm for a particular item, I'm willing to accept 500-2k lower depending on various circumstances and to discount further future hassles with crazy customers.
A final word, much like propagated in Bollywood movies where the heroine's pleas of NO's are only considered as postponing the inevitable, people across various platforms think the same applies here as well - kabhi to maanega apna offer!