3. - 1. It must be serious, and such as may be demanded: if, therefore, a person were to sell me an article, and by the agreement, reduced to writing, he were to release me from the payment, the transaction would no longer be a sale, but a gift, Poth. Vente, n. 18.
4. - 2. The second quality of a price is, that the price be certain and determinate; but what may be rendered certain is considered as certain if, therefore, I sell a thing at a price to be fixed by a third person, this is sufficiently certain, provided the third person make a valuation and fix the price. Poth. Vente, n. 23, 24.
5. - 3. The third quality of a price is, that it consists in money, to be paid down, or at a future time, for if it be of any thing else, it will no longer be a price, nor the contract a sale, but exchange or barter. Poth. Vente, n. 30; 16 Toull. n. 147.
6. The true price of a thing is that for which things of a like nature and quality are usually sold in the place where situated, if real property; or in the place where exposed to sale, if personal. Poth. Contr. de Vente, n. 243. The first price or cost of a thing does not always afford a sure criterion of its value. It may have been bought very dear or very cheap. Marsh. Ins. 620, et seq.; Ayliffe's Pand. 447; Merlin, Repert. h. t.; 4 Pick. 179; 8 Pick. 252; 16 Pick. 227.
7. In a declaration in trover it is usual, when the chattel found is a living one, to lay it as of such a price when dead, of such a value. 8 Wentw. Pl. 372, n; 2 Lilly's Ab. 629. Vide Bouv. Inst. Index, h. t.; Adjustment; Inadequacy of price; Pretium offectionis.