Platinum is only 300k in the UK AND HAS ALWAYS BEEN! Check Blur/Oasis et al in the 90's or Kylie's first albums UK stats in 1988 for that matter!!
It's a crime Body Language has only sold that many! It's an incredible album - one of her best.
I think the figures for both X and Aphrodite are fair though. X was a mess musically but does have a couple brilliant tracks, and Aphrodite was a mess in terms of promotion - I think that whole album was treat as a vehicle for her tour - which was stunning! Get Outta My Way should have performed much better though