Is a person held accountable if, when asked about the price of a commodity, they state a price other than its real one in order to purchase it for less than its value?

If a person is asked about something they do not know, they should say: "I do not know," based on the Almighty's saying: "And do not pursue that of which you have no knowledge." However, if a person is knowledgeable, it is forbidden for them to tell the questioner something contrary to what they know, based on the Prophet's (peace and blessings be upon him) saying: "Religion is advice." The questioner can work as a broker for the seller, selling the commodity for a specific fee.