Chewing gum aids in oral hygiene, it has utility. The opportunity cost is hardly anything. The opportunity cost of something that exists purely for aesthetic purposes is 100% of the cost of the good. In this case you're talking $1,000+ for a watch. I am always reminded of the scene in Schindler's list where he looks at the additional things he could have sold or gone without to save lives. On my death bed I don't want to look back with regret and wonder how much more I could have done to help people if I wasn't acting selfishly.

To me the moral level of consumption is as close to the minimum required to survive and make an optimal economic contribution to society. Everyone needs happiness and entertainment in their lives. The struggle is avoiding excess.