All perfect praise be to Allah the Lord of the Worlds. May His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
Islam enjoins Muslims to be honest and ties this with fearing Allah the Almighty. Allah the Exalted says {What means}: " O ye who believe! Fear God and be with those who are true (in word and deed)." {At-Tawbah, 119}.
Islam has legislated preemption right to ward off harm that could befall partners in case one of them sold his share to a stranger. Jurists stated that the right of preemption entitles a person to buy a property with the same price determined in the first sale contract. This is because contracts are based on what is apparent so as to stabilize transactions.
Al-Shirbini stated: "The person claiming preemption takes the share from the first purchaser for the same price determined in the sale contract." {Al-Iqna`, V.2:337}.
In conclusion, since the above piece of land was registered in a price lesser than the actual price it was sold for, the partners aren`t obliged to pay more than the registered price save if there is documented evidence proving otherwise; in which case the partners become obliged to pay the true price. According to the Jordanian Civil Code, the party inflicted with harm due to preemption right, which entitles the new buyer to get the property for lesser than the actual price, may file a suit. Article (1163) states: "Every dispute regarding the actual price of the property for which the right of preemption is claimed shall be settled through court and the latter may give the person claiming the right of preemption one month to pay the price it has determined or his right to preemption is extinguished." Moreover, the affected party may take this to court. And Allah the Almighty knows best.