For your used things for sure, the seller being reputable and the items being less common works well. Common items (like that knock off Switch dock above) that can be faked are tough because even if you buy product X from seller A, all product Xs can be in the same bin at the warehouse and Amazon just grabs one and ships. if Seller B is pushing a hard-to-distinguish knock off that Amazon believes is product X, then one might end up with that one and think seller A is to blame. That sort of mistake is definitely Amazon’s fault in my view. You can end up with knock off stuff when buying from the official brand’s store on Amazon for crying out loud.