Can't you just also sell some random cheap crap (perhaps via drop-shipping) to pad the activity on your account and avoid having a bad rate of returns?

I mean, you could, but you'd still just continually be paying for returns on faulty items over and over again.

I dont know how much the user paid to get my pi returned - but it couldnt have been much. They are pretty light and fit in a small envelope. It wasnt rush delivery or anything.

I imagine if the rate of return was 80%, and eBay didnt ban you, youd make money (minus your time)