In the jargon of big companies, what does it mean that ducks don't talk?

People who sell things in the market are reluctant to sell things. "Ducks don't talk" is a traditional large-scale commercial jargon, which is used to describe that people who sell things in the market are unwilling to talk or sell goods at a reduced price. In large-scale transactions, buyers will judge whether the quality and price of goods are reasonable by observing the attitude and behavior of sellers. The seller's "duck doesn't talk" will make the buyer feel hesitant or distrustful, thus affecting the transaction.