Homemade polarimetric synthetic aperture radar drone

I have made several homebuilt radars and done some synthetic aperture imaging testing with them on the ground. I have wanted for a long time to put a radar on
a drone and capture synthetic aperture images from air. When I last looked at this few years ago, medium sized drones with payload capability were around 1,000 EUR and up. For example in Low-Cost, High-Resolution, Drone-Borne SAR Imaging paper by A. Bekar, M. Antoniou and C. J. Baker, the imaging results look excellent. They used DJI S900 drone with a list price of about 1,000 EUR. The price for the whole system is quoted to be £15,000, which is a way too high for my personal budget even just for the price of the drone. Many other papers use similar style medium sized drones designed for carrying cameras and they are usually equipped with RTK-GPS for accurate positioning.