Is your frt diff leaking or seeping? I have seen high lifts like yours cause a vibration even with a dble cardon shaft loosen the 3rd member. from what you are saying it sounds more like worn gears.. I would not call the cost of this Job out of line with the parts you said were changed. The grease is high I normally use 3.5lbs of moly I pack the whole Knuckle keeps water out even more needed in the south. and 1 lb of wheel bearing . I'm not understanding the 2 charges that seem to be for the same part . I charge from 6 to 12 hrs on a knuckle job for labor .But I clean everything change studs. replace hardware clean and repack birfs bearings races etc etc.. Hand Torque everything. I can do one in 3 or 4 hrs with ugga duggas and kinda clean. But I prefer my knuckle jobs to last another 20 yrs . I would not be to mad about cost other than the dble charge . I would be pissed about it being mis dianoised and sitting for 2 months on a max 2 day job. I woud have never blamed a knuckle job for the noise your defining.. I would be chase gear lash and driveshafts then t case Im sure your pinion angles are wacked.. Good luck