Aww, I love yarn falls! Apparently they cost so much because of the time it takes to do them. It's cheaper if you buy your own yarn, but not by much - you're looking at at least £100 I'd say, and about 6 hours work... You absolutely must post pics when you get it done though - I'm hoping to have mine done soon too, I'm thinking black and electric blue (luckily I know someone who needs the practice and will do it for free)