When I was working in an instrument calibration shop a while back, one of the jobs we often did was repair and calibration of vacuum gyros - both horizons and DGs. The mechanisms are more robust than the equivalent electrical instruments but it is much more difficult to set up the erection system. Typically, it would take a skilled, trained bench technician, equipped with all the proper tools and a RPY table, a couple of days to strip, clean, replace damaged bearings (you have corrosion in there, right?) and jewelled pivots, then reassemble, coarse adjust and calibrate the instrument. Each time you perform an adjustment you have to seal the case, run the gyro up to speed and check the erection rate and final attitude. If any adjustment is needed you have to re-open the case, adjusting and repeating the process over and over again until its back in specification.
So, you reckon this is too expensive? How much do you reckon your friendly neighbourhood bench technician is worth? Two dollars an hour? ten? fifty?
...and if you get disoriented at night like that Kennedy chap, how much does a funeral cost?