Costco was always the price leader in Melbourne as well.

They import their own petrol supplies, or used to when the original owners owned it but I think they sold the business a few years ago.
Would have to check on that.

am

"Good to see Costco providing competition for the big two supermarkets."

I think you'll find that the supermarkets are generally the price leaders in most places so not sure why you think

they (the supermarkets) are the enemy.