At the beginning of Doctor Faustus, Faustus takes a closer look at the collected wisdom of centuries of scholarship and has only this to say: codswallop! Instead, he turns to magic not only for the power and wealth it can bring him, but also because of the forbidden knowledge it promises to reveal to him. In the end, Faustus doesn't care about the knowledge itself—just what it can do for him, and that kind of thinking is exactly what winds him up in a pact with Lucifer. So while Faustus may be knowledgeable, the play suggests, he's certainly not wise.
Wisdom and knowledge are not the same thing, and maybe if Faustus had gotten that idea through his thick head, he wouldn't have sold his soul to Lucifer. Maybe.
Faustus's evaluation of knowledge focuses upon whether or not it can provide him with wealth and power.