If one of Young, Stroud, Levis or Richardson are worth that much of a haul, why wouldn’t Lamar be? Granted, rookie contracts certainly provide significant surplus value, especially at the QB position. So I guess that really would be a major factor, still. You just have to do better than merely 2 firsts for Lamar.
He might be indeed be worth that much to someone else, except he's also looking for fully-guaranteed money.