Oldfield , 660 F.2d at 212-15 (“[T]o validate [this] approach in our eyes, the owners would have to establish that royalty rates are in fact fixed in the marketplace by a process which parallels [the expert’s] calculations.”); see Foster v. United States , 2 Cl. Ct. 426, 448 (1983), aff ’d , 746 F.2d 1491 (Fed. Cir. 1984) (“situations where income producing potential is a key element for both buyer and seller . . . in arriving at a fair price”); Whitehurst , 337 F.2d at 775; Cementerio Buxeda , 196 F.2d at 180; see also Sowards , 370 F.2d at 90 (“whatever method is employed, the evidence offered must have a bearing upon what a willing buyer would pay a willing seller for the property on the date of the taking”); cf . Kimball Laundry , 338 U.S. at 5-6.