That WAR calculation could underestimate the free agent price since it would be a loophole that lets players spend an uncapped resource. No penalties. Teams over the luxury tax line pay a penalty. This would be money they could spend for WAR without a penalty.
It has been more than 20 years (1996) since the famous quartet of Travis Lee ($10 million, $5 was bonus), John Patterson ($6.075 million), Matt White ($10.1 million), and Bobby Seay ($3 million) were free agents. They were picked 2, 5, 7, and 12 so were higher picks. But those bonuses might suggest a free agent today would go well north of $20 million.