Article 460 of Civil Code

1 - Failure to mention the price shall render the sale void if it appears from the agreement or the circumstances that the contracting parties intended to transact at the price current between them or at the market price. 2 - The market price at the time and place of sale shall be the applicable price. If there is no market at the place of sale, the place whose prices custom dictates should apply shall be considered. All this shall apply unless otherwise agreed.