As far as I know there are no other monitors on the market right now that are capable of 4K resolution. It's expensive because it's so new and cutting-edge. I hope you also realize that you will need a LOT more power to play your games at the same performance as you would get in 1080p.
You will be able to use this monitor as a TV as long as you have compatible inputs, which will be HDMI and Displayport in this case. But your TV shows and channels will still be in 1080p, because the world simply hasn't caught up.
EDIT: If you're using a cable box, you shouldn't have to worry about attaching a TV tuner.