I guess it depends where you get your figures from. Let's just call all of them sales behemoths.
But when you say Floyd haven't sold much since The Wall, you don't mean time-wise...their albums sales are constantly high. I guess you mean the albums post-Wall haven't sold much, and arguably The Wall was the last Pink Floyd album proper.
I granted Bowie in my earlier post, he even did a Drum-n-Bass album...but Radiohead? Don't make us laugh. I really like them, they're maybe in my top 10 favourite musicians, I could easily name 20 songs as favourites...but in comparison to Floyd they're about as ambitious as Status Quo:
- no songs longer than 6 minutes and no genuinely-proggy structures, with one famous exception: Paranoid Android.
- very little avant-garde experimentation when compared with the Floyd discography.
- very few instrumentals.
- only one main singer, who after a while does sound a bit samey, as good as he obviously is.
- some albums sound alike to each other, they have had the same sound since In Rainbows: that over-reverberated sheen. It's very lush, but not ambitious. Jonny Greenwood alone is more ambitious than his band.
Definitely - The Final cut was 90% a Waters solo album - Momentary lapse, Division Bell and Endless River are a totally different entity - Similar to post Fish Marillion same name - almost same line up - very different music