Justin E. H. Smith in his blog:
Such disdain forms a central part of the founding myth of Western philosophy as told by Plato in his relation of the trial and execution of his mentor Socrates. Here we learn that Socrates has been wrongly charged by the court at Athens on what may be reduced to two principal counts: that he teaches doctrines, and that he accepts money for this teaching. The denial of the first charge is important to the story we would like to tell here, too, but we will return to it soon enough. As to the second charge, Socrates protests: “As little foundation is there for the report that I am a teacher, and take money; that is no more true than the other. Although, if a man is able to teach, I honor him for being paid.” Socrates relates of a certain teacher named Evenus that he would admire anyone who “really has this wisdom, and teaches at such a modest charge. Had I the same, I should have been very proud and conceited; but the truth is that I have no knowledge of the kind.”
Thus philosophy, on this understanding, cannot be remunerated, because there is no real exchange, at least if this is thought of in terms of the offering of goods or services. Philosophy does not give its adepts a new body of knowledge, but only leads them through a dialectical method that shows what they already knew, or thought they knew, in a new light. There is nothing to sell here, and thus nothing to pay for.
Except that philosophy often does quite a bit more.
More here.