Is it permissible to increase the price of an item beyond its original price in exchange for the effort expended in acquiring it?

The agent is obligated to act in the best interest of his principal. It is not permissible for him to benefit from anything except with the permission and knowledge of his principal. If he informs him of the true situation and that he will profit from it, then there is no harm in him increasing the price. Otherwise, it is not permissible.