There are many ways in which communities can both help themselves and play a role in their social environment by getting involved in collective buying and bargaining.
Since a community can convene to represent a large number of individuals, it is also possible to use this representation to bargain or organise to acquire goods and services for a reduced price.
The first thing that comes to mind is collective buying of food and household goods, building materials etc. But the sky is literally the limit: communities can negotiate for collective discounts on energy, tax, literally anything that members agree and are willing to try.
In addition, communities can promote collective buying and negotiation of prices and become providers of certain goods and services to the wider community.
Having checked the price of some simple goods like fluoride free toothpaste or coffee on Amazon.de it seems clear to me that this may be a way to acquire these goods for a better price than through retail outlets. As to the ethical implications of doing this through Amazon, that is a matter than needs our consideration. Certainly, some suppliers of organic goods are already providing online services for collective buying. This is probably worthwhile looking into.