The actual printer unit I'm using (i.e. not including the Arduino components) is $50/£40 and is increasingly available:

https://www.adafruit.com/products/600 http://www.sparkfun.com/products/10438 http://proto-pic.co.uk/thermal-printer/

See https://github.com/freerange/printer/wiki/Making-your-own-pr... for more information...