The dry weight of the [steel/aluminium] engine for a Cessna 172R (117kg) is about four times the dry weight of the entire recommended setup for a Mugin-5 Pro, and the airframe of this UAV is carbon fiber. Some of its steel/aluminium fittings/fixtures that need to handle high stresses look like they would be difficult to replace with low-radar-cs materials, and there is a fair amount of avionics dotted around plus the four VTOL motors, but it's a really paltry amount of radar-reflective material compared to the average light aircraft, and I'm sure you could mitigate that somewhat with radar-absorbent materials/structures.
The idea of relying on fighter jets/attack helicopters/SAM systems shooting these things down sounds like an entirely asymmetric and unsustainable state of affairs.
Reading the article I thought they should have started in VTOL mode somewhere near the cost, then dive down onto the sea and fly like a https://en.wikipedia.org/wiki/Ground-effect_vehicle over the mediterran, climbing up at the other coast and again land in VTOL mode. Now I know ground effect vehicles are a lost art, but I would think collision avoidance and evasion would be simpler to implement by computer vision on-board, while operating autonomously between waypoints and without remote control.
The idea of relying on fighter jets/attack helicopters/SAM systems shooting these things down sounds like an entirely asymmetric and unsustainable state of affairs.