But you need to factor efficiency into that. If the top speed of the chopper is 100mph, versus 10mph for the drone. Then you can cover a much larger area quickly, furthermore a helicopter can stay up longer and has much greater range. So it's not enough to say a heli costs x/per hour therefore drones. Kind of like saying trash trucks are expensive, therefore we should replace them with wheel barrows.

From the article: We were asked to search a large area of farmland with the drone. I covered three-quarters of it using three batteries, and the last quarter was a little too far for me to get good first-person view reception

Landing to change batteries every couple of minutes, is a serious blow to efficiency.