I don't think it's really meant to compete directly to start with. This is a technology PoC that will be initially be used to deliver small, "I need it now" packages to locations that are easily air-accessible but might be a pain to get to via driving. In the future it's likely this will be a complement to normal ground-based delivery for heavier packages and packages in high-density areas, probably with a "mothership" ground vehicle or small local warehouse as a base of operations.
But an inner city context is exactly the worst for drone delivery. Where do they drop it safely? How do they navigate to that low an elevation around high rises, awnings, trees, overhead wires, etc.? How do they avoid pilferage or outright theft? Animal damage?
I have no numbers but if executed properly it should reduce the number of people required in the total delivery process and it should in faster delivery.
