Under $200. Single 2S LiPo battery. Readily available parts. Programmable flight control via Python.
Take the eduMIP and hook it up with the DSTR app in order to control the Mobile Inverted Pendulum from your very own cell phone!
A smart thermal camera using FLIR Lepton3 on BeagleBone Blue board. The project won the "FLIR Lepton3/BeagleBone Blue challenge" in 2017.