Stickers?
Price is not so much the problem, it's weight.
The lightest class of quadcopters ("TinyWhoops") are in the sub-30 gram kind of range, often 18-25g
A GPS receiver typically weighs ~5-10g
With these things typically having a flight time of 2-3 minutes, adding another 25-50% or so of weight is going to seriously reduce that flight time and performance of the quad, and that's not even considering where to mount the bloody thing
Meanwhile, fixed wing aircraft are treated totally differently - for example, there is legislation coming in whereby you can fly a fixed wing up to 1000ft, but a quad is only allowed to 400ft.
If it really were about reducing the possibility of AirProx events, then this makes zero sense - how is a fixed wing less likely to hit an Aircraft than a Quad?
Biting the hand that feeds IT
