Although not an AWAC, but more of an airborne radar, which , fulfills the requirements of min. mid range i.e. 200Nm, low level / small rcs threats, such as drones and CM's, at a fraction of the cost of an aircraft borne radar, are the
"Aerostat Radar Systems".
It's coverage is not limited to just low flying threats, but all flying threats, as well as ground / sea threats, plus communication relays, if configured to do so, as is the case with Atlas systems.
Usually filled with Helium, they have been known to be deployed up to 15,000ft.
They have been deployed at sea as well, but due to rapid weather changes have proved to be challenging.
With Drone tech evolving rapidly, this technology might become obsolete within a matter of years.

Basic Concept

Israeli Atlas Specs

ELTA ENA-2083 radar

A US Border Surveillance post