Louisiana Civil Code Tit. VII, Art. 2464. Price, essential elements

The price must be fixed by the parties in a sum either certain or determinable through a method agreed by them. There is no sale unless the parties intended that a price be paid.

The price must not be out of all proportion with the value of the thing sold. Thus, the sale of a plantation for a dollar is not a sale, though it may be a donation in disguise.