Fair market value in a voluntary licensing transaction between arms-length parties ordinarily lies somewhere between the two poles of cost to the seller and benefit to the buyer. That is, the seller will not ordinarily charge less for a license than its anticipated cost, and the buyer will not ordinarily pay more for a license than its anticipated benefit. In the case of a hypothetical license, it is often difficult to determine what, at the time of the infringement, the seller and buyer thought would be their respective cost and benefit.