Walmart isn't a budget grocery store, though. Its prices are higher than actual grocery stores (like Safeway.) Also, everyone is WAY cheaper than Instacart.
The answer to this is complex, it has any number of products that are cheaper than products of similar quality from any other store. Places like Safeway/Aldi typically beat on price on very generic items that may or may not have similar quality.
The biggest thing to watch for at Walmart is price discrimination dependent on location. Back in the days I used to shop with them (read made less money) picking a store in a poorer neighborhood could save $10 to $30 dollars on the same car of items.
The only place that competed with Walmart on price for me was WinCo.