I get this information by virtue of an EE and extensive training in microwaves courtesy USAF.
Entirely different methods used to amplify power and amplify a received signal - especially with microwaves.
They DO make them but because they incorporate an LNA (low noise amplifier) the cost of a "proper" microwave bidirectional signal booster is far beyond these RC amps.
https://www.pasternack.com/pages/Featured_Products/coaxial-packaged-bi-directional-amplifiers.html
So just going by what I know is available I do not think these systems costing $250 are using these type amps meaning the receivers are not designed for low noise (signal quality) nor low level - such as by a drone 4 miles out with a 50 mw transmitter. Most amps of the $250 variety simply shunt the received signal straight through because in their intended configuration BOTH sides have the boosters.
Never forget snake oil salesmen are still alive and well.
Exhibit 1:
EMF Adapter - EMF Protection for the Home & Office