A Slave performed minor tasks for Caesar hoping for his freedom. Caesar turned him down saying he must pay more than a token for freedom.
You need to pay a fair price for what you want.
During a visit that Tiberius Caesar paid to one of his country residences, he observed that whenever he walked in the grounds, a certain Slave was always a little way ahead of him, busily watering the paths. Turn which way he would, go where he might, there was the fellow still fussing about with his watering-pot. He felt sure that he was making himself thus needlessly officious in the hope of thereby gaining his liberty. In making a Slave free, a part of the ceremony consisted in giving Him a gentle stroke on one side of the face. Hence, when the man came running up in eager expectation, at the call of the Emperor, the latter said to him, “I have for a long time observed you meddling where you had nothing to do, and while you might have been better employed elsewhere. You are mistaken if you think I can afford a box on the ear at so low a price as you bid for it.”