Between a price that is obviously too high and one that is obviously too low lies a zone where no one really knows the right figure. A trader's skill is the ability to work well inside that zone of uncertainty and come out ahead.
In a peddler's market, the main contest is not between rival sellers, as it is in an economy of firms. It is between the buyer and seller facing each other across a single deal, each trying to pull the price their way.
Where there are no fixed price tags, a price is a guess each side makes about what the goods are worth and what the other will accept. Price is something worked out in each exchange, not a known figure both sides already share.