Is 8% considered ghabn (exploitative overpricing/underpricing) in a manufacturing contract (Istisna') for a construction project with materials, and is the exploited party (maghbūn) allowed to request annulment of the contract four years after its signing and two years after its completion, according to the Hanbali school of thought?

The questioner's statement: "a manufacturing contract for contracting with materials" is ambiguous, and the true nature of the transaction cannot be definitively ascertained, because contracting for materials could be either an ijarah (lease/hire) or an istisna' (manufacturing contract). Resolution No. 129 (1/14) of the International Islamic Fiqh Academy states that a contracting agreement (aqd al-muqawalah) is permissible, whether the contractor provides both the labor and the materials (istisna') or provides only the labor (ijarah for labor). If the contractor provides both the materials and the labor, then the Academy's Resolution No. 65 (3/7) regarding istisna' applies.

As for the early Hanbali jurists, they did not discuss ghabn (excessive deception/disadvantage) in istisna' because they did not recognize it as a distinct category; rather, they discussed ghabn in sales in general. They stipulated that whoever has knowledge of prices or was hasty in selling and did not pause, has no option of choice due to ghabn, because there was no deception (taghrir), as stated in Kashshaf al-Qina' and Sharh al-Zarkashi. The criterion for ghabn that establishes the option of choice according to them is what deviates from custom; they did not specify a particular amount, though some estimated it at one-third or one-sixth. In case of dispute, recourse must be had to the Sharia courts for adjudication.