Labor and land prices in more affluent areas will be higher, so it is expected COGS will be higher.
However, Walmart now displays in store and online for pickup prices on their website. I walked into the Walmart and paid $1.11 more than if I were to have ordered it via the app on my phone or website for pickup.
And Walmart was very upfront about it, and I knowingly paid $1.11 more because their online order and pickup option sometimes makes you wait 20min+ for a Walmart employee to come out and give you what you bought (even after it says your order is ready for pickup).