How is it not relevant to the topic in question? I am not saying that one is more prone to be scammed by buying one of these. What I'm saying is that the hardwallet is like a giftcard that has been loaded with 'money' already and someone can decide that they don't want to use it anymore, and therefor sell it.
Good grief what are you on about now? That is exactly what you were saying.
On that note, the flaw with these "Bank notes" is that they are still handled by human beings, so there will always be the human element to take into account and, as I'm sure you're aware, throw a stick in the wind these days, you're going to hit a scam or someone trying to take advantage of a lack of education. This is a problem; a very serious one.
There's a smartphone app that you can verify the card with. The keys are inaccessible and you need to have physical possession of the card to redeem it. This is a system that makes it next to impossible to get scammed if you buy one of these.
The online wallets that are used in Crypotcurrency are secure only because it is keyed to you and only you. No-one else can access it without your private key. Also, with cold wallets, like the Ledger Nano for example, there are various conditions that one has to meet before accessing anything on the wallet. That being said, if one decided to sell their Ledger Nano as second hand, my previous argument would then come into effect. What would stop the person selling the Ledger Nano from accessing the wallet after selling it to you, as the private key on that cannot be changed after initiation? This would further emphasize my point of a lack of education, as anyone who is sufficiently educated in using hardwallets, would never buy a second-hand wallet anyway.
It's totally irrelevant but you can reset the seed on a Nano S and if you buy a second-hand one it is essential you do so. These devices are completely different as the key is encrypted inaccessable
There are various website to facilitate the buying and selling of unwanted gift cards already, so what's stopping those websites from adding these "hardwallets" to their database and facilitating the buying and selling of these?
Why would anyone buy one online when they could make a blockchain transaction? These are only designed to be exchanged face to face. There's nothing to stop these sites advertising $100 bills and then sending out fakes ones. Is that a flaw in the concept of cash?