The unfortunate part here is the local brick and mortar stores (Target, Walmart, Walgreen's, etc...) charge higher prices than Amazon for most products. This is primarily the reason I shop online.
If I need something now from a local store and absolutely can't wait two days for an Amazon Prime delivery, I get in my car and go pick it up. With Prime, I can even get discounted next-day for an added $3.99/item.
And then there's the available streaming video service that keeps getting better.
I guess the only advantage Google is selling here is the same-day delivery. The price per product will most likely be more.
Yes, they could charge less for their same-day delivery serice, but unless Google plans to become a distributor and build some warehouses around the country then offer discounted prices on products, they aren't competing with Amazon Prime.
No comparison should even be made between the two.
Google is simply selling a same-day delivery service.