I have a Mamiya 6 75mm lens with a spot of damaged coating. I can get it replaced for $120, which...given the cost of this system...isn't that awful. Bob Watkins (Precision Camera Works) said that it wouldn't impact image quality. I've included a picture. The spot is in the 12 o'clock position. Is it worth getting this fixed?
That small white-ish dot? I wouldn't worry about it. It will not affect the sharpness of the lens, and not cause any noticeable abount of extra flare even if you shoot wide open.
See it this way: That tiny spot has lost its coating, so now that spot is transmitting 96% and reflecting 4% of the light compared of the rest of the surface that is transmitting 99,5% and reflecting 0,5%. Not a problem, especially when that spot is less than 1/10 000 of the surface.