In the UK Amazon has a deal with supermarket chain Morris ons for groceries orders and deliveries through the Amazon website. My understanding is that a significant portion of the groceries sold at this new store are Morrisons'.
I don't know if this is just a coincidence but there's a Morrisons supermarket almost opposite this new store in Ealing. They could wheel the stock over the road in a trolley if they wanted!
And it costs significantly more to get the exact same egg box from Amazon than from Morrisons... (They have slightly redesigned labels)