Yeah. The crazy jobs (like bezerker) require 2500cp. Would be very difficult to get otherwise.
Tier 4 jobs are locked behind a grind worse than guild war characters. Wouldn't worry about not having enough CP for those.
The money is in the drops you get. The gold coins are worth 1000 and the gold drops are 5000.I may be a bit jealous.
btw: I don't get any Rupie from coop. Is it because high level players always join my room and kill the monsters too fast?