Whether your co-op can buy cheaper than Colesworth retail prices is a different matter.

Some people are willing to pay a bit more if it means supporting a community store over a big corporate one.

I'm living in the USA now, and there's a lot more supermarkets here. In my area in California, there's a few local chains with 3-4 stores, some co-ops, and the major stores. The biggest supermarket (Walmart/Sam's Club) only has 20% market share, and even the top 5 companies (Walmart, Kroger, Costco, Albertsons and Ahold Delhaize) still only account for 44% market share. The top 3 in Australia (Coles, Woolworths, and Aldi) account for around 75% market share.