1. Bionic hadn't had the "lowest sales ever for a #1", even at that time there were albums at No. 1 selling less.
2. No. 1 alone isn't an achievement anymore, especially when it drops heavily from the 2nd week on, nowadas it's the chart performance as a whole that matters.
3. Christina Aguilera came from a Platinum album (300k) to Bionic (60k). So Bionic sold a 5th of what Back To Basics did. Her "standard" is ~ 500k (Christina Aguilera got Gold, Stripped got 5x Platinum), Bionic is ~ 1/8 of that. Alexandra Burke came from a 800k-album to HOH which sold ~ 20k copies so far (up to now 1/40 of Overcome).