There are more moving parts. Not only is there a rear diff, there is a front diff, centeral drive shafts, front dirve shafts, four tires to replace versus two rears, (front ribs last much longer as they are not powered) then there is also a top deck to contend with.
My b4 everything was in the rear of the buggy out in the open. My b44 I had to remove the top deck, front bulk head, center drive shafts, just to access the differentials. Then becides rebuilding two diffs, there were also 12 bearings to replace rather than 6. (6 in each diff)
Though I only replaced them once (all by choice) it was rather expensive.