Not sure what theyve based these predictions on. If you look at their last album sales these seem way off for some.
Lil Waynes last album - 217k
Kendricks last album - 242k
So 500k for both is wildly optimistic
Kanye did 328k last time so 300k makes some sense. But I think he's lost a lot of fans since then. One direction have peaked and are on that downward slope. 400k will be great at this point. Boybands have a shelf life.