I might point out a couple things before spending that kind of money. I distinctly noticed a lack of warrantee! I also noted the statement that he produces no finished product (he only sells gears).
It is also interesting that for better than half the price to do a repair professionally with proper calibration cleaning and lubrication, he is getting all the money with none of the risk.
We used to provide gears, but getting good results for extented periods requires more than one will get doing it the first time. We got into speedo repairs because we got tired of doing it over when we sent them out. For a few years we only changed the level of discomfort as we were doing them over ourselves. The proper cleaning, lubing and evaluation of wear is critical to getting the number set to work properly.
Bosch Master, ASE Master, L1
33 years MB technician