Landscape Review
Summary
Drone package delivery as a technology has been proven for several different payload categories to date, but as a commercial industry it has yet to establish itself, mainly due to regulations.
From a commercial perspective, the lowest hanging fruit for drone delivery seems to be medical and cooked food. This is because they are light weight and time sensitive. The components to support this payload weight of around 2 kilograms, have considerable overlap with more established applications for drone use, namely data capture from onboard sensors, making them readily available and relatively cheap.
An established industry for drone package delivery for larger payloads of 20+ kgs is still in its infancy, making any off the shelf heavy lift drones($10-20k USD) or service offering relatively expensive compared to consumer level drones.
The componentry and software required to build a custom drone capable of carrying a payload of 20+ kgs exist. A custom build would be cheaper than an off the shelf heavy lift drone, though it would require more time to integrate all the components.
Commercial Offerings
There are a few different types of commercial offering available in the marketplace.
Multirotor Delivery Drones
In place of building your own drone, companies like Heven offer heavy lifting drones in a multirotor frame with all hardware and software included. This sort of drone is what can be replicated in a custom build.
Picture Courtesy - Heven