If the long term goal is to sell items directly there is plenty of room for margins.

Combined with Google Now, you should rarely ever run out of anything you need.

I like thinking about how an urban environment re-arranges itself when you remove the need for most store fronts, and driving.

ATMs, CVS/Walgreens/Duane Reade, Target, Best Buy; these are all places that probably won't exist in the volume they do today in eight years. Whether it was low interest rates or other factors that made them multiply, it won't really matter. A mobile phone + a neighborhood distribution center should be all that is needed. Automating checkout won't be enough. (In an ATMs case, cash just won't be used except may be for narcotics.)

What happens to Starbucks, McDonald's, and other chain food service is a whole other question.

Collecting data about customer purchasing habits is valuable in the aggregate. Shopping Express links that data more general data about the customer's habits on the Web, etc. In some cases this will enable Google to serve the customer better, and in some cases this will enable Google to serve advertisers better.

Since its membership based, I imagine the same as amazon prime - when you have a cheap/easy/just awesome way to get a product, you are more likely to use it to purchase things in the future.

They saw Amazon Fresh, and are skating to where the puck will be. I'm guessing if it puts pressure on Amazon, it's worth it even if Google doesn't make big margins.