Sapphire is not all that much better than the mineral glass in most watches, and I would assume the same is true for the IonX glass in the

Watch. It certainly is not $200 better. DCRainmaker, a guy that tests fitness watches, claims to have never had an issue with scratches on any of the watches he has used, most of which are not sapphire. It was in reference to the sapphire fenix 3, which he sees little reason to spring for over the mineral glass.
Sapphire, all around, may be better, but it isn't $200 better. Now as a whole package, maybe, but I wouldn't base the decision on sapphire alone. In fact, in a sports/fitness situation, I would almost say you may prefer the shatter resistance over scratch resistance.
I think most of you are falling for the sapphire name and marketing. Yes, it is really good at resisting scratches, but it is also very brittle, and I believe, has a lower level of clarity.