Without knowing who specifically you are referring to, I am pretty sure I know at least one you may be referring to
There is one seller here who most frequently sells “Via PM”.
Not a big fan of dickering. I mostly buy at ask or simply move on. But there are all kinds of sales threads for all kinds of buyers
I must say though, the super aggressive pricing seller, I haven’t even looked at in years
I usually list my books at less than GPA myself and I don’t leave much room except for the low ballers who I don’t want to engage with
Tend to buy the same way. If my price is significantly less than your ask, I will move on