Then go try to sell bank issued gold bar with a scratch back to the bank for approximately the same price as you paid for it.
Maybe it doesn't work the same in all countries but the general rule still looks like that.
You obviously have never owned any gold so why not stick to topics where you have a clue what you are talking about?
No bank or bullion dealer will pay you the exact same price as they sold it for or they would go out of business very quickly (taking out spot price variance)
There is always a buy/sell spread, typically I but at 2% - 3% over spot and if I were to sell immediately back to the same dealer I would get around 95% - 100% spot depending on demand at that time.
Bullion is called bullion for a reason, here is an example:
https://www.hattongardenmetals.com/sell-scrap-gold.aspxSee how prices are based on gold content with no mention of scratches?