I think what they mean is every calf born in America is a donor "prospect". Buy a calf and flushing it, makes it a donor, BUT not neccesarily donor quality. I'm sure every embryologist in America has seen a cow get loaded off the trailer and thought " I guess they decided to bring a recip along" and then the owner says " ain't my donor awesome" as he hands the embryologist a handful of cash, ET guy says "she looks like she'll work nicely".
All it takes is a couple of people new to the game thinking that a donor "prospect" means that the calf is the next great one. They get in a bidding war and all of sudden she brings 2X or 3X what the calf should've brought. Probably doesn't work everytime but obviously worked for them or a buddy once upon a time.