Buyer made aware of dishonesty in tawlia

What if he (buyer) is made aware of dishonesty in Tawlia (i.e. the seller claims cost price, whereas not so)? Is there a difference in opinion between Saahibain regarding this mas`ala?

Dishonesty by seller

A person sells his wares for a profit, and the buyer assumes the seller to be honest in what he claimed, then the buyer is made aware of the dishonesty of the seller (i.e. he sold it for more than what he claimed). What is the ruling here?