Is it permissible to distinguish a broker who has put in greater effort and incurred additional costs in selling a property from other brokers?

It is permissible to give a broker who has exerted greater effort a wage that exceeds that of other brokers, provided that the person from whom this increase is taken, whether the seller or the buyer, is aware of and consents to it. This is because brokerage falls under the category of a "ju'l" (stipulated reward), which requires the consent of the one who pays it. However, taking this increase without the knowledge of the owner of the money is not permissible, as it constitutes consuming people's wealth unlawfully.