I tend to justify this based on usage. I haven't worn a watch regularly since, well, never really. Maybe for a few months here and there. But I don't view this as a watch. It's something else. A wrist computer.
Back to usage, it'll be on my wrist all day every day and charging at night. It's always available for use constantly. No, it won't be on constantly but it has the ability to do what my iphone can't. Notify me. Moreso with reminders than anything else for appointments. Messages or calls, second. I miss a lot as it is. Usually it has to be muted.
A quick glace at my wrist because it nudged me, yep, need to do that. I don't need everything work related coming at me, but I would like what I value and that varies for everyone. You can customize this.
Anything else is just gravy IMO. Maps while hiking, not having to hold your phone. Leaving the phone charging at home and taking calls on watch. And probably the list will go on.
I remember when push email was a big thing. I think of a smartwatch as push iphone notifications because I'll actually see them in more of a real time basis. Many Blackberry users wanted the iphone to have a blinking light for alerts. Screw that, the watch is the ultimate notification center.
Anyways, 12-18 hours every day of using a wrist computer is easily worth as much, if not more, as an ipad that I hardly used. PC-->iphone-->smartwatch. Forget ipad, enter smartwatch. With lesser use, forget annual iphone updates, it'll be every two years.