Few years back, I experimented with quadcopters drones and FPV (First Person View flights). I was able to use a 5.8ghz (Wifi) transmitter and receiver up to 800 meters (the system can even go further).
After letting go of that hobby, I converted the onboard video system to a target camera. It worked really well. But if you are in to it, you would need little bit of knowledge of electronic and soldering (nothing too complicated).
All you really need is a camera, a TX (transmitter), an Rx (receiver), a TV screen, batteries, a tripod and a case to carry it all. Maybe $200 box. So maybe not that cheaper after all.
Here is a video showing my 1/2 mile trip. Nothing too exciting, except the video quality at max range.
https://youtu.be/6Z0bMZa0Lr8