How about the iPhone? Many 'imitations' yet people who don't really know any better by the Apple product. "I don't want a fake" is very likely the reason.
In that case, though, the UI and details actually create a different user experience. As a professional software engineer, I like to think that I "know better" on various criteria.
I've used Android phones and while they are fine enough, the UI feels a little 'off' and the responsiveness is lower. It's enough to make a real, subjective difference.
I like to think that I got an iPhone after carefully considering all the alternatives and making an informed technical analysis because I am a unique individual and I would never follow the herd or copy other peoples' actions. (At least that's what I tell myself.)
YOu could try to claim 400M. But each quarter, half the sales are upgrades. So maybe, what, 100M? Which is 1/4 of America. But all the sales aren't America.
Maybe 25% market penetration? Not small potatoes, but still, Most people haven't bought one.