Napkin-math time: I see 4 motors, searching the model-number suggests each has a max draw of ~380 watts, so let's assume it averages 1000 watts in operation, for 6 hours a day, with a local cost of electricity at $0.20 per kilowatt-hour, and this continues for one month.
1000*8/1000*$0.20*30 = $36 per month per drone.
That's not give-a-penny-take-a-penny territory.
I previously pointed that out to someone in another comment, however I did not use 50 because the video-presentation continues with:
> The current in the power-line was approximately 300 amperes [...] a higher power-line current would result in a proportionally higher charging power. As future iterations of this system become more efficient, the ratio of time spent flying and time spent charging will significantly increase.
The point remains that once you reframe the electrical situation in financial terms, you will realize it is not just gleaning discarded ergs, and is instead significant enough to raise questions of theft and justice.