The advantage of their integrated LCD and Arduino is that it would only use 2 pins instead of the 6-7 that would be occupied by the shield you linked. This would allow you to connect other shields and have more room for add-ons. I agree that $89 is steep though, hopefully that price can come down as more are made.

I don't understand how this board only "uses 2 pins". The schematic shows the ezLCD component still uses 7 pins for I/O. Using the SPI bus requires 4 pins and the other 3 are presumably for the touchscreen sensing. The board still has the full Uno footprint, so you could connect other stuff to those pins at the same time, but you couldn't do anything with them while driving the LCD.

There is a PIC24f that does all the graphics processing, and the arduino talks to it through serial. the spi connection is used to program the atmel . the other connections are optional for use like a interrupt on touch .

Dallas 1-wire? Haven't looked at the schematic or anything else, but that's an example of an interface that just requires 2 connections - signal and ground.

That's not what this uses.

You could do it cheaper but you would run out of code space quick taking care of the graphics. on the arLCD the onboard PIC Micro takes care of all the graphics. You just tell it where to put a widget and it takes care of the rest .

The arLCD is 3.5", whereas the $39.95 from Adafruit is 2.8". That still shouldn't account for the price difference though.