It's the potential buyers who carry some of the blame as well.
Communication is the key.
If as a seller I want an offer I will post $100/OBO
If I want the $100 I post that price.
In both cases people will ask what is the lowest you will go.
Well the answer is simple. In example #1 I will take the best offer.
In example #2 it's $100
Buyers are as much to blame.
And if people are buying to resell great for them. I have sold items like that before BUT I would rather sell to a collector for $35 than to a reseller for $35.