Small drones are everywhere. At times I think they blot out the sun. And they are very inexpensive -- The highly rated Black Falcon 4K camera drone only costs $99 to $199.
But this paper is not about low-end drones, it is about medium sized high-performance drones that cost anywhere from $tens-of-thousands to $hundreds-of-thousands. Their primary customers are various defense agencies, but they also have many interesting civilian applications. An article in Forbes alerted me to these and what is probably the builder of the most advanced design, which is just starting to take off.