I purchased approx. 20 lbs (which is like 1/32 of a cow). It was my first time doing this, & I'm telling you, it's so worth it! I'm definitely going to do it again. The cuts are already packaged by the butcher; you just stick all of it in the freezer, defrost it the day before you cook, and it's AMAZING! It also turns out to be a lot cheaper than buying grass-fed beef from the store; mine turned out to be about $4 a lb.
There's also a Chicago Meatshare group on meetup for those who are interested.