chiefs have Jadon Sancho theory as Dortmund hold firm on £108m valuation

Who fixes the price on these players, because obviously there are players like Kieffer Moore that are being sold time and again for less than their true market value. Is it not fraud when football clubs and their employees lie about the worth of their stock? If so, why are they getting away with ripping off Kieffer and his family, is the whole of football that corrupt?