A large number of buyers see a price, want the card and pay the price. If they don't see a price, they then either walk or have a hissy fit. For transactions of this type there should be a DFZ.
Other buyers will routinely see a price, want the card and offer less. If the seller doesn't comply, both parties either walk or have a hissy fit. If negotiation ensues, then this type of listing does not belong in a DFZ.
Other buyers will routinely ignore the price, want the card and make a lowball offer. If the listing price is much higher than market (and the seller knows it), a deal might ensue but is extremely unlikely, but can occur. Making a reasonable lower offer on a BIN (without the OBO option) can result in a deal. Here the BIN is essentially an irrelevant price.
So what is a seller to do. Basically this is influenced by a number of factors.
Does he need the cash yesterday? If so, he prices for a quick sale.
Does he price exactly at market price and wait for the first "I'll take it" while fending off multiple offers for less?
Does he price a little above market to be able to accomodate reasonable "hagglers" that are BTH?
Does he intentionally overprice thinking that when he announces a "price drop" he will attract bargain hunters? Have you ever been to Hawaii where all the shirts for tourists are 50% off?
I would venture to say that everything we have is for sale if the offer is high enough. Motivation to sell is extremely variable.
Conclusion Recipe
Mix many types of buyers with many types of sellers.
Create a BST with as few rules as possible placing restrictions on the market itself. No price, no problem. High price, no problem. Lowball offer, no problem. DFZ, not needed. BTH, why not.
Let free market economics work in the real world.
I will not buy from every seller, nor will I sell to every buyer, but I will sell anything I have one way or the other.
Footnotes:
DFZ = dicker free zone
BTH = born to haggle