had previously suggested that Hejira was the last album that the general public bought; a new theory is that DJRD sold poorly because it was a double album. Lots of double albums did/do poorly (the White album, T'log); I believe there is too much new material to digest properly - It's not the right "chunk" of new material.
DJRD sold over 500,000 copies ("gold"), I recall reading, in its first year of release. While not a big hit, that's still rather significant, especially back in the 70's when multi-million (multi-platinum) albums were somewhat rare.