The price put upon "I don't have to go figure out what a good monitor is and what are good input devices".

For some people is pretty much priceless.

Also there's no cables to connect the monitor and the device making it all one thing you can pickup and move around, which people value as well. Also the difference between (900+$monitor+$mouse+$keyb) and $1700 is really not a lot of money for a lot of people, especially those people considering an Apple devices.