I wholeheartedly recommend that you DO buy a quarter of a cow from a farmer. If you have the space, get a half. If you have friends who will go in on the order with you, get the whole steer.
We started out with a quarter of a cow and it lasted us a good while, although we wished we had gotten the half. If we had gotten the half, along with the half a hog and the pastured chickens we got from another farmer, we wouldn't have needed any other meat for the whole year. As it was, we ended up having to still buy some meat at the store before the season came around again, but considerably less than we would have otherwise.
Now granted, it cost more than it would have if we had gotten the on sale stuff at Safeway, but it was less than it would have cost us for the same quality beef at Whole Foods. We also felt good about supporting a local farmer who practices humane and sustainable farming.