The underlying principle is much the same as that which lies at the base of the equitable theory of consideration in the law of trusts—that he who has fairly paid the price should have the beneficial use of the property. It is no answer to say that AP spends its money for that which is too fugitive or evanescent to be the subject of property. That might, and for the purposes of the discussion we are assuming that it would furnish an answer in a common-law controversy. But in a court of equity, where the question is one of unfair competition, if that which AP has acquired fairly at substantial cost may be sold fairly at substantial profit, a competitor who is misappropriating it for the purpose of disposing of it to his own profit and to the disadvantage of AP cannot be heard to say that it is too fugitive or evanescent to be regarded as property. It has all the attributes of property necessary for determining that a misappropriation of it by a competitor is unfair competition because contrary to good conscience.