The beautiful case it's in cost £10 and the SD card containing the OS costs £5 so a computer for under £50. However all of the above are optional. You can download the OS for free and go without a case (I wouldn't)
I've had this sitting on our table for over a year thinking about what I should do with it. I still haven't decided what to do with it, I'm thinking I should build a laptop/computer for Nate.