Emergency deliveries in rural areas are where this will be most useful. Getting medicine and mechanical parts to remote places during crisises is hard.
My bet: the military/security/coast guard, for far off service posts (like when they put hydro wires way out in the middle of nowhere), offshore Oil, and for very specific things (i.e. medical equipment) for remote communities.
There is room for this in the supply chain of many firms. There’s a lot of industries where waiting for something can be very expensive.
Most companies and their parts suppliers are in cities, wherein there are any number of efficient modes of transportation - to the point wherein 'a drone' wouldn't even make logical sense, let alone economic.
There's going to be a considerable overhead associated with operating them - control centers, NOCs, etc. etc. so it might very well be that the 'lack of a human' is the real differentiating factor, i.e. safety, risk.
Nobody is going to be flying 'fresh ingredients' anywhere on those drones, there are regular planes for that as well.
So the use case of 'landing on a moving sheep' is probably right up their alley: it's remote, far, and landing on a moving ship is very dangerous. So it might be the killer use case for something like this. Remember the ship would have to be fitted with a permanent lading spot, trained crew etc. etc. so it would have to be used for something needed consistently.
This is critical, as it's almost impossible to hold a sheep stationary while landing a drone on it.
There's definitely a place for "cheaper than helicopter" delivery, even if it is only where things have gone so horrifically wrong that paying almost any price is worthwhile.
However, not so sure I agree that economics will prevent 'fresh grocery' delivery. It will be different vehicles for sure, but the operating costs of a small electric vehicle with 5-10lb payload can be very low (cents/hour). I doubt there's going to be direct farm-to-house deliveries, but instead something that can augment the current transportation infrastructure. Imagine a national grocery chain adopts small electric drones for last-mile delivery. They leverage existing shipping network in place to keep stores stocked, and just send drone deliveries from store-to-house. Actual flight cost for one round-trip store-to-house is going to be pennies.