Funnily enough as mentioned in your original post; I collect drones, upgrade, and build them. I usually go for a cheaper approach to finally create a drone that costed me 300$ which is about as good as a 700$ drone.
My recent make was: The chassis and engine of a Syma X8G (Bought at 110€ at black market), a custom Quanum Q-2D Gimbal (Overall steadier view, but also allows mounting multiple possible cameras),(90€) and a Xiaomi Xiaoyi 1080P 16MP Sports Camera (110€) along with some custom legs I had lying around somewhere.
And for that 310€ build I basically made a 700+€'s worth drone with the most random parts I could find. Hobby has died out because I'm saving up for my car though.