What is Quantum Valebant?

Legal Definition
Quantum valebant is a Latin phrase meaning "as much as they were worth." It is a common count at law very similar to quantum meruit. The two legal actions differ only in that quantum meruit is used to recover the reasonable value of services rendered, while quantum valebant is used to recover the reasonable value of goods sold and delivered. This count is considered a type of assumpsit.
-- Wikipedia
Legal Definition
As much as they were worth. In pleading. The common count in an action of assumpsit for goods sold and delivered, founded on an implied assumpsit or promise, on the part of the defendant, to pay the plaintiff as much os the goods were reasonably worth. 3 BL Comm. 161; 1 Tidd, Pr. 2.
-- Black's Law Dictionary
Legal Definition
As much as they were worth; one of the common counts for goods sold and delivered. See Common counts. See, also, 3 Bl. Comm. 163.
-- Ballentine's Law Dictionary