I have a 2005 19' Keystone tandem axle travel trailer and (yes I know) never serviced the axles. I pumped some grease into the zerks every few years, but haven't repacked the bearings or adjusted the ...
If you told them what you posted here... They are likely quoting a worst case scenario. There is really no way to tell just what is needed without someone getting their hands dirty. Since you have been pumping grease into them, you may have a greasy mess in there.