That's not how Google Express works. Do you live in the bay area? You have to see the ops yourself.
Membership is $95/yr, $35 min, $3-5 for rush delivery.
They get the same data feed as anyone else, just check Curbside's website and see how their Target product listings are the exact same items and same pricing.
Most of the available items are only pantry stuff, cans, jars, boxes. You can splurge but it's gonna be rare to hit $300 buying $2 to $8 items to get there.
Costco has the ball most together. They've carved out a section just for Express deliveries. Boxes, tapes, most of the common items are already stocked. Costco employees are assigned to Express duty, pick, pack, and leave it for the Express drivers to pick up. Easy peazy.
Local delivery is commoditizing to about $5 per delivery, Postmates just dropped to about $5, DoorDash is about $5, whoever's dispatch makes their vig of a few percents just by matching demand to supply. Google's strategy is just dominating by putting the big capital investments into the fleet whereas the other guys have to rely on iffy relationships with 1099 contractors.
How is this different from Webvan?
Lots and lots. The unit economics are there.
Will this work?
Yes. But only when you have the money to wait and last it out and have an automated car trick up your sleeve.