Welp my 4k tv was cheaper than a lot of the 1080p tvs. And I would agree with you wholeheartedly, depending on the situation of the consumer.
If you use more than just your Xbox on your tv around half the time (cable, sat, etc...) or use a computer to watch YouTube videos and the like, then the upgrade definitely isn't worth the cost, especially if your old tv is working fine.
The reason I switched comes down to, that I use my Xbox for about everything. Games, shows, internet, music, blah blah blah. I don't watch TV/sat at all. And since my new 4k was under 400$, that means When Scorpio comes out (at the projected 500) I'll have a setup capable of 4k, 60fps, on a 55 inch screen for under 900$.
Not for everyone, sure. But it'd be hard to get more use out of it than I would so I'm going for it. Once more unto the breach, dear friends. I shall see you from the other side.