Here's a tip: Instead of buying those expensive rolls of butcher paper, ask your local newspaper about purchasing their end rolls. They are literally the end of the roll of blank newspaper.
The Sacramento Bee sells them in 3 different widths and they have a ton of paper on them. Up side: Super cheap. The largest width is roughly the same size as standard butcher paper and is only $2.25 at the Bee.
Down side: It's newspaper, not butcher paper. It's not as durable. But it still works great for most art projects. I love to use it to cover the kitchen table for a disposable table cloth the kids can color on. I also like to tape a long strip of it up on the wall outside our apartment so the kids can paint murals.