A guy that gets his trucks inspected at the same place I do just got a 550 4x4 6L TQshift with a 9' PTO dump for $51,000. He added a 9'2" Western V plow and a tailgate salt spreader and squeaked in under $60K.
Hard to believe I paid $35,000 for my 450 4x4 7.3L auto with a 9' Tamaqua aluminum dump just 6 yrs ago.
They're nice trucks if you need a small package. As an M/D owner, I can tell you they can be kinda cumbersom in some spots.
The 4500/5500's look like a nice compromise. They'd be really sweet if they could figure out how to get them with 4x4 & airbrakes.