Ok so I'm trying to make an RC/autonomous aircraft of some sort, I'd rather make a multirotor but I'll settle for a fixed wing for now if I must. In assembling the components, I've already got an Arduino Uno clone, a good motor controller that can control up to 4 DC motors, and can get a Wii Nunchuk for about $5 for XYZ gyro input. Now I see project plans for UAVs that are claimed as "cheap" for $500? Really I don't see what else I'll need than GPS and RF communication.

Can someone suggest plans that actually are really cheap, based on what I've got?