Our big grocery retailers, all two of them, have online shopping with at home deliveries.
They charge different prices for the same item.
Hence for each item you want it will be cheaper at one store.
But not all your items will be cheaper at the one store, there will be a split.
You create... a website that sits above the online grocery retailers and takes your complete order. Rather than having it fulfilled at one place it splits the order such that the grocery items are ordered at the one they are the cheapest at. You save, maybe.
Problems,
1. You double up on delivery fees.
2. You pay a further commission to the umbrella site.
3. Maybe not enough discrepancies to make net bill cheaper.
