You forgot that sellers can’t even leave negative feedback about buyers now.
As a buyer I film unboxing videos for myself for expensive purchases. As a seller I don’t sell anything more expensive than $100 or so, and after hundreds of sales I haven’t had a return yet (knock on wood).
For more expensive items above $100 I might film a boxing video, though, and if I ever did get a return on that item, I’d film an unboxing video as well. At least I could prove if a buyer mailed me back a brick or whatever. Of course it’s also entirely possible that eBay staff don’t even bother reviewing the evidence.
I’ve been buying and selling since the late '90s. I stay away entirely from areas rife with fraud, like computer parts or things teenagers might want to buy, and so far it’s worked out for me.