Yarn for Lyric Tree?

[butshesdead]

I'm interested in knitting this pattern:
http://www.etsy.com/view_listing.php?listing_id=15152226

But I don't know what yarn to use.

I really like how the Brown Sheep Burly Spun looks and the color.
But I can't afford $15 a skein.

I've searched through Ravelry already and can't decide.
What do you think would be a good alternative?

[KnittinHoney]

Webs has Cascade Revolution on sale for $3.29/ball:

http://yarn.com/webs/0/0/0/0-1001-1294-1323/0/0/4627/