[chongli]

but if you look at the location of most big warehouses (e.g. Amazon, Walmart) they're built outside of big cities for cost reasons, so now you have to fly twice as far to deliver packages onto the opposite side of the city

Big warehouses are dependent upon current transportation technology (trucks and big cargo ships). If drones become feasible, there's no reason we couldn't move to decentralized (retail-scale) warehousing serviced by drones.