All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
There is no harm in selling the shop for more than its value as long as there is consent between the seller and the buyer. There is no specific percentage of benefit in Islam that the tradesman should get when selling his goods provided that he does not cheat nor deceive the buyer, as in such a case it is forbidden. A Muslim trader should always remember the saying of the Prophet : "Allaah is merciful towards a person who is lenient when he sells, buys or asks for his right." [Al-Bukhari]
Allaah Knows best.