I'm going to offer my two cents here so please do not take it the wrong way.
The beauty of group buys is to purchase grain in bulk and save money on ingredients. This is pretty obvious. In my humble opinion, if anyone is looking to get in on a group buy for less than, say, a third of a sack I think they should strongly consider buying from their lhbs. The amount of savings on small quantities is insignificant but you are still supporting your lhbs. Again, this is just my humble opinion and people are free to choose and buy in the group buys as they please. $0.02